ASE doc

Hi everyone. Before I dig into the trans again, I just want to post up a quick story of what's been done to this unit and what happened this weekend. 3 or 4 years ago, 3rd gear went out. The 2-3 shift was starting to slip and it was obvious before the final failure that the 3-4 clutches were going. I rebuilt the unit and went to great lengths assuring that the 3-4 clutches were as strong as possible.

I installed the Sonnax Smart Tech input housing that replaces the factory snap ring and backing plate with a bolt on plate. With the new housing, I installed all the pieces to maximize 3-4 clutch capacity. I installed an 8 stack of thick BW hi energy green clutches with thick steels. I installed the Transgo 2-3 kit, along with a billet 2nd servo and Sonnax 4th servo.

Everything else in the unit is new super duty and I took extra care to make sure it all went together with proper clearances. I installed the unit with an Edge 3,500 10" converter. Line pressure at full throttle 3,500rpm in 3rd gear after the build was 285psi. Since then, the trans has continued to shift excellent. The 2-3 shift is as solid as the 1-2 shift. Then, this weekend, right after one more perfect 2-3 shift, I slowed down for a car turning in front of me. Returning to the 2-3 shift point, there was no 3rd gear. I have 1st and 2nd, no 3rd. I can't imagine that the 3-4 clutch has failed. There was no sign of any slipping. Like I said, the last 2-3 shift was just as solid and perfect as they have been since the build.

One weird thing is that my speedo had stopped working prior to 3rd gear leaving. I checked out the cable and was thinking maybe the cable was broken or had come out of the speedo head. Now, it seems like the very moment I lost 3rd gear, the speedo started working again. I'm wondering if there might be a problem with the speedo drive gear and retainer. Maybe the retainer got into the governor gear and peeled the teeth or locked up the governor gear.

I'll get the car down to the shop this week sometime and do a pressure test. If pressures look good, I'll pull the tail housing and look at the governor and speedo drive. I can drop the pan and air test the 3-4 and forward clutches too.

If anyone has any thoughts on this, please reply. I'll take any shared ideas into account when I start my check out on this later this week.

ASE doc

No reply from anyone? As common as this problem is, I expected to hear something.

A friend replied to my post on another hot rod forum. He dashed my hopes of this being caused by the governor gear. He said what I had thought, the gov being stuck or inop would cause a loss of all shifts. I'll check that along with pressures, but he thinks I've probably lost the 3-4 clutches again. Only 6K miles on an assembly that should easily handle 200hp, more than I'm putting through it. I'm wondering if maybe something in the valve body either got pinned or gave way.

Either way, at this point I'm going to tear the unit down to see how everything is doing. The fluid in this trans is perfect. No sign of even being hot. Fluid condition is the primary indicator for me in all the trans issues I diag. There is a very slight trace of friction material, but that's to be expected.

I've had the idea in mind for a while to replace the VB the next time I have the pan down. The VB in the unit is old and shows sign of scoring and wear in some of the bores. The same local guy who did the pump that's in there now also does valve bodies. He does excellent work.

If the 3-4 clutches have gone again, it's time for some serious research on what happened. This unit has shifted great since I built it 2 1/2 years ago, including the last shift into 3rd. I may have noticed a slight bind a few times. I thought it must be the 3-4 clutches applying before the 2nd servo is fully backed off. It only ever did this on light throttle up shifts. If this has caused the clutch pack to go out this quick, I'll definitely go alot further on the next build to be sure it doesn't happen next time.

The last time the 3-4 clutches went, there was ample warning. Soft 3-4 shifts was the big clue. None of that this time around.

I'll have the car towed to the shop on Friday and pull the trans. Update to follow.

ASE doc

Just got a call back from Dana at Pro Built Automatics. What a great guy. Really knowledgeable and no BS. He agrees that the 3-4 clutches would hardly have failed without some slipping/slow shifting before hand. On a factory input housing, the lugs can blow out of the case on rare occasion, but he agrees that on the Sonnax Smart Tech housing, that's next to impossible. I think I must have either blown a plug out or stuck a valve in the valve body.

I'll know for sure this weekend. Thanks Dana for being there for me.

OrangeBird

iTrader: (1)

I saw your thread and hoped someone who knew these transmissions would have answered too , I was kinda waiting to see what the cause was gonna be . I do have one question , what do you mean by "blown a plug out" ? Are there press fit plugs that seal passages off in the valvebody ?

ASE doc

Hi OrangeBird. There aren't press in plugs in the valve body but in my case there is a thread in pipe plug where there would have been a 3rd gear pressure switch installed. I know it's a stretch, but maybe a possibility. Dana mentioned that even with the governor gear peeled, the trans would still shift at high enough revs. I never did fully test that. I think I'll try really early tomorrow morning to run the car into the shop. I'll see if it will shift if I let it spin up to 6,500. I may have also pinned the 2-3 shift valve, or stuck a check ball. There is one spot in the case, where check ball #8 (2nd clutch) goes, where the steel check ball that a prior builder had installed beat up the aluminum pretty good. I've worried that the plastic check ball may get stuck there some time. That ball getting stuck might cause just what's happening. I may drill that spot in the case and put a small pin there to prevent the ball getting wedged.

I'm only thinking out loud and putting together ideas so I have a plan to follow as I start digging into this thing tomorrow night. I'll do a pressure test before I open things up. The pressure readings should tell me something. A line pressure drop in 3rd would mean that something is blowing off pressure.

Only about 5-6K miles on this thing since I put it together. Hell, it's practically brand new.

ASE doc

Well.............. Guess I didn't exactly lose 3rd gear, just misplaced it. I apparently found it again this morning. Seriously, I drove the car into the shop this morning for another road test and so I could dig into the trans tonight after work. The trans shifted fine, as if there was never a problem. There has got to be something wrong in the valve body. Or maybe the big check ball and capsule in the servo housing stuck. The 3rd accumulator check ball will require tear down to replace, and even then it's no picnic. I'll do some testing tonight, then drop the pan for inspection.

I will order up a fresh valve body from Portland Trans Warehouse either way. If there is alot of friction material or any metal in the pan, the trans is coming out for tear down. Otherwise, I'll swap in the new VB with the 2-3 shift kit installed and see how it works.
Talking with Dana and also with Glen at Transgo, I am now thinking of swapping the Superior billet 2nd servo for the Sonnax super hold. The Sonnax servo will likely work better with the Transgo shift kit and resolve the bind that I have gotten a few times on light throttle 2-3 shift.

I understand now from talking with Glen why it happens. I always run the car in man 3rd or I just manually shift it. Love the B&M Megashifter. When the trans is in manual 1st, 2nd, or 3rd, the overrun clutch is engaged. The bind happens when shifting from 2nd to 3rd, when the 3-4 clutch starts to engage while the 2nd band is not fully released, and the band struggles against the overrun clutch. If the overrun clutch wasn't engaged, the trans would simply engage 4th for a split second until the band released.

Glen's advice was to switch to the Vette servo, or if I really have to have the Superior billet servo, put a heavier release spring on it. I think maybe the Sonnax servo would be a good compromise between the two. I'll talk more with Glen today about 3rd gear's return and also with Dana, before I decide which way to go.

OrangeBird

iTrader: (1)

Wow , It came back ? Ya know , of all the automotive problems I ever worked on , the intermittent was always the biggest PIA . I'm sure when ya rip into it you'll find something and I like your idea of stuck valves VS anything actually broken since it went and found third when you least expected it was going to . I will be interested in hearing what it actually ended up being , I am by no means any kinds of 700R4 expert , more like someone with a casual understanding of it , and I'm always looking to learn more .

ASE doc

UPDATE: On the way home Friday, I did some testing of the 3-4 clutch, and it failed. It seemed to shift firm enough at first, but then after putting some load on it in 4th gear, it let go. The clutch is definitely gone. This means that for all my hard work, I got something wrong in the set up of the shift timing.

I was pretty bummed at first. I'm really trying to move steady towards my 383 build. My plan is still to install the Eddy Pro Flow XT intake this next spring, then start putting funds away for the motor build. So, this side road back into the trans is definitely inconvenient.

As I prepare for the redo though, I'm actually kind of excited to go in and see how everything is doing. Then to reprogram the 2-3 shift, rebuild the 3-4 clutch pack and try this again. Actually, everything is basically new and I'm only rebuilding the 3-4 clutch, cleaning things up and replacing the overrun clutch, since it will probably be burned. The cost will be around $250. Not bad. The fluid is still fresh, not burned. I'll just clean things up, check bearings and air test everything, then put it together with new gaskets, new filter and new fluid.

I'll be ordering parts on Friday or Saturday. I'll do the work the next weekend. I'll post up with what I find when I get into it.

ASE doc

There may end up being a delay before I do this repair. Finances and the looming end of the rodding season here in rainy Oregon might delay any further work on the car.

I always hate to see the end of summer, putting my Beasty away for the winter. The up side is that garaging the car means less expense while I drive my beater Suzuki Swift back and forth to work. This means more money for parts. I have alot that I want to get done next year. Hopefully I can get all the parts together over the winter.

I also have projects like the exhaust system that I started this year and haven't finished yet.

1982Z28Modified

Having just rebuilt a 700R4 and installing it in my 82 Z28, I am by no means an expert, but I did learn a few lessons along the way.


It sounds like you did all the right things to ensure the 3-4 clutch would last forever.


Your line pressure at WOT is 285 which is great. What about at idle? Part throttle? Your post doesn't mention anything about shift kits or other mods.


Start with a TRANSGO SK 700 Corrects/Prevents/Reduces: Absolutely prevents Stuck TV valve. Late shifts, downshift clunk; 3-4 clutch failure; no lockup; 2-4 band failure; early shifts; 1-2 slide/slide-bump; reverse delay hot; 2-3 cut loose; reverse clutch failure. "83-87 Valve body, Kit lets you make Torque Converter lockup-no wires or electrical needed". Also the "Corvette servo" 7-2P kit. Finish it with the 7-500 kit which will give max line pressure all the time.


Your 700R4 will be bulletproof after that.

ASE doc

Thanks Modified for your reply. Minimum line pressure is 125 psi. This is higher than generally recommended(70-95 depending on who you ask). I did this to make sure there is plenty of apply pressure on the 3-4 clutch cruising at low engine speed. The main concern with high base line pressure is heating up the fluid. I have a monster cooling system on the trans to keep the fluid nice and cool.

I have the SK700 kit installed. I actually have a custom built pump from Oregon Converter. The guy there does them from a late pump body and really does them up nice. It came with the high rev spring installed and clearance set. The high rev spring pretty much eliminates the worry of broken rings by preventing pressure wobble. I went ahead and put the steel rings in anyway.

I have the Sonnax line boost kit which includes a heavier TV spring than what TG provides in their kits, along with a .500 boost valve. I also have a .296 lo/rev boost valve. I installed the TCI blue reg spring as it is the stiffest I could find. I shimmed up the TV spring to set minimum line pressure. This build wasn't my first rodeo.

The mistake I made starts with overthinking the build and going off script on the Transgo instructions. If I had just either refreshed the build that was already done to the unit, maybe a few tweaks to fix issues, it probably would have worked fine. Especially with the high test parts, like the Sonnax input housing, I put in. If I had done the Transgo 2-3 shift kit, which anyone who manual shifts their 700 should really consider, and followed all the instructions without "customizing" it, I probably would have been fine.

I didn't do either of those things. I went all out on the biggest servos etc. to make this thing a beast. The problem I've run into is using the big Superior 2nd servo, the largest apply area 2nd servo you can put in a 700, with the TG 2-3 kit. Right now, I'm even questioning if I didn't swap the return spring for a lighter one to increase clamping force. I'll find out when I tear it down. The problem here is that the 700 already relies on the cushion springs to start the 2nd servo release. There is no release of 2nd apply pressure on the 2-3 shift. So the 3rd accumulator oil, with the help of the springs, has to overcome the 2nd apply oil to force the servo back. The vette servo has about a 2:1 ratio of release area to apply area. Transgo takes this servo and adds heavy cushion springs to help start 2nd servo release. The Superior 2nd servo has practically a 1:1 ratio of apply area to release area. In a non Transgo modified transmission, it relies on a heavy return spring to produce a correct 2nd servo release rate.

The Transgo 2-3 kit has you drill a vent hole in the 3rd accumulator circuit at the 3-2 shift valve that makes the task of releasing the servo even harder. This makes the Superior servo an issue when used with the TG 2-3 kit. This is what caused the drag shifting from 2-3 that took out my 3-4 clutch. It doesn't help that I always manual shift this thing. That puts the overrun clutch in the mix and if shift timing isn't perfect, clutches will burn.

I've been advised that somewhere between enlarging the servo release hole and installing a stiffer spring, I may be able to make the big servo work. The better solution is to switch to a different servo. I like the Sonnax 2nd servo. It's in between the big Superior unit and the vette in apply area. It uses the factory style cushion springs and it has what looks like a 1.5:1 release to apply area ratio. I've been advised to install it with a coast clutch servo spring from a TH400(heavier than the factory release spring) for best results.

I'm really wanting to keep the big servo that I have now. If I open up the unit and find something else wrong that explains the issues I've had, I may just keep it in there. I don't right now though. I'll probably buy the Sonnax servo and make the decision on which one to use once I'm in there.

I've found something that everyone who works on one of these units should read. It's the -700R4 Principles of Operation-. It's the original 700R4 training manual from GM for their factory techs. The book sells for $35 online but I found it in a free pdf download on a Suburban forum. A hint on finding it, use a Google search for 700R4 principles of operation. Couldn't find the free download through Yahoo. It has a complete and detailed description of the gear train and hydraulic circuits and clears up any questions on how each part of the unit works. It helps make sense of the performance modifications we make and why they work. It's taken some time for me to absorb the info, and I do this kind of thing for a living, so expect to spend some time reading and reading again. I find it easier to focus on one area or one circuit at a time.

Studying this manual really opened my eyes as to why this build didn't work. I took the Transgo 2-3 kit mods and drew them into the hydraulic circuits to get a better picture of the changes. I still have a question or two but I am alot closer to fully understanding the 700R4.

jmd

iTrader: (4)

You've made for a good read. I bet you'll have things sorted soon.

Pseudo-related; It was really fun & educational for me to read the Sonnax article on powerglide servo pin bias with regard to a balance on apply & release. Which, seems to be a little bit related to what you're working towards instead of going to a different servo.

ASE doc

Thanks jmd,

I'll look for that Sonnax article. It may be educational for me as well.

More studying today, I finally understand what Transgo is doing with the 3-2 valve in the 2-3 kit. It is a hint that they refer to it as a "low valve". One of the holes they have you drill routes manual low oil from the manual valve directly to the low/reverse clutch, bypassing the 1-2 shift valve. Another hole routes manual low oil to what was the 3-2 valve. Their "low valve" has a plug blocking the outward end of the bore, so that the low apply oil acts on the valve, pushing it open against the spring. When open, the valve vents governor pressure. This will help hold manual low by preventing governor pressure from acting on the 1-2 shift valvetrain.

I still am not fully certain of the entire purpose of the .110 vent hole that they have us drill in the 3rd accumulator circuit at what was the 3-2 control valve. The change of the valve from 3-2 control to a manual low governor vent alters 3rd accumulator oil control during the 3-2 detent downshift. In factory form, the 3-2 valve is opened by spring pressure during the low speed 3-2 shift, allowing for quicker 3rd clutch and accumulator release and quicker apply of the 2nd band. At high speed, the 3-2 control valve is forced shut by governor pressure and 3rd accumulator oil is routed through an orifice. This slows release of the 3rd clutch and accumulator along with apply of the 2nd band.

Enlarging the 3rd accumulator orifice decreases the effect of the 3-2 valve on shift rate at high speed, but with the Transgo low valve in place of the 3-2 valve, it is likely they found that the enlarged orifice by itself wasn't enough to allow for a quick, clean 3-2 downshift. That would be why they have us drill the vent hole. I believe it is this vent hole that messes with the release of the 2nd servo on the 2-3 shift, without plenty of spring on the servo to help force it back.

I'm still not done studying this thing. I want to be sure of what TG is doing in this shift kit and what if anything can be done to improve the 3rd accumulator circuit and 2nd servo release.

ASE doc

Update: Continuing my research into the hydraulic controls of the 700R4, as modified by the Transgo 2-3 shift kit. I have been talking to a friend on another forum who is very knowledgeable on these units. He reminded me of something on the 2-3 kit. I posted above concerning TG's deletion of the 3-2 control valve, replacing it with a "low valve" that essentially vents governor oil in manual low to help hold low gear at high engine speed. I was under the impression that the vent hole TG has us drill in the 3rd accumulator circuit at the 3-2 valve bore actually vented 3rd accumulator oil. This is not the case.

What I wasn't considering is the separator plate plugs that TG has us install. They have us plug hole 9, which is the 3rd accumulator circuit to the 3-2 valve. By plugging this passage, we close off the 3rd accum circuit before the valve. Therefore, the vent hole we drill in the 3-2 valve bore does not vent the 3rd accum circuit but simply vents oil that leaks across their low valve. With the mods made in the 2-3 kit, the 3rd accum operates at full rate at all speeds. The 3-2 speed modulation that the 3-2 valve provided for smooth easy shifts in stock form is eliminated. The mods are intended to and should provide the quickest possible 3-2 and 2-3 shifts at all times.

I feel much better knowing that the vent hole isn't a leak in the 3rd accumulator circuit. I was having a hard time getting my head around that. Unfortunately, this doesn't help explain why the big Superior 2nd servo has issues with the shift kit. Perhaps it is just because the shift kit produces faster shifts and the big servo, due its large swept volume, simply doesn't move that fast.

Again, all of the factory servos, and the Sonnax servo(while its ratio is closer to 1.5:1) have a ratio of apply area to release area that favors the release side. This, along with the cushion and return springs, is how the servo is released against 2nd gear apply pressure, that doesn't vent in 3rd gear.

ASE doc

I'm getting closer on my parts list. I plan on getting the Sonnax servo here, so that I have it on hand. I am going to give the big Superior servo one more shot though before I shelve it.

Hopefully, in the next month I should have photos and a complete list of mods, in addition to the TG 2-3 kit.

ASE doc

It doesn't look like anyone is following this thread anymore. I'll still follow through to the conclusion so that the information is here for others who want to know about how the Transgo 2-3 kit works and are looking for some input on their own 700R4/4L60 build.

The instructions can make the kit mods seem really complicated. I know that I got lost at first trying to make sense of it. Once you sit down and look at the changes made, having good technical information on the factory design at hand for comparison, the kit mods become clear and the results of the kit are really very simple.

Here is a rough sketch of the 3rd accumulator circuit as modified by the TG kit. Once you understand the modified circuits, you see how shift rates between 2nd 3rd are determined by the size of the two orifices pictured.

To make sense of the circuits and the changes, and for comparison to OE, have a copy of the TH700 Principles of Operation handy. Below is a link to download the manual for free. If you want a printed copy, I have found them online for about $35. This is a bargain on a must have technical reference for anyone who is serious about building these units. The Principles of Operation training manual goes way beyond the service guide, explaining the principles of the design, "how it works". The hydraulic diagrams are broken down to explain how each shift and shift modulation is accomplished. The gear train is also dissected and very thoroughly explained. Studying this book helped me makes sense of the performance mods we do to make the trans shift more firmly and how we boost line, along with clutch apply, pressure to make it hold up under higher torque loads.

I own the factory service manual(Helms) for the car, which has a great section on the 700R4. I also have the ATSG manual for the 4L60/700R4 1987-1993. The ATSG is pretty much a reprint of the 87 factory manual section on the automatic trans, with some update information that is vital for a good build result. The ATSG book is also inexpensive and saves wear and tear and grease smudges on the expensive factory service book. The Principles of Operation completes a very good set of technical information for this unit.

www.1990suburban.com/repair_and_service_manuals/700-R4_Automatic_Transmission_Principles_of_Operation_2nd_Edition.pdf

paulo57509

I'm following along...thank you for posting.

Since everyone has or will lose their 3-4 clutches someday, it's important to have this kind of detail available for those of us that like to know the tech behind the mods. Even for those that just do stock rebuilds at home, knowing the fundamentals of operation is vital.

When I was doing my 4L60E rebuild with a Pro-Built HD kit, I stumbled across an electronic copy of a tech publication (I "think" it was a GM training publication). I've been looking for a similar one for the 700R4/4L60.

ASE doc

Hi paulo, Yes, this is the GM training manual(circa 1983) for the 700R4. I haven't seen the book for the 4L60E, but then I haven't looked for it. I remember finding pages from this book posted on different forums before. I feel lucky to have found the entire book.

There are so many different techniques and as many different opinions among the experts on how to build these units for performance. The key to success is starting with a good system and parts combination, like the Pro Built packages. Then, once it's together, if there is any flaw at all in the shifting, don't just try to live with it. Go back in and fix it before you end having to replace clutches again.

My build is especially tricky because I manual shift the trans alot. That requires perfect shift timing to keep it alive.

paulo57509

This is how I felt when I received my Pro-Built kit. The kit wasn't just a hodge-podge of off the shelf stuff just thrown together. It contained full and what seems like partial kit parts needed to address specific weaknesses.

I just looked at the 4L60E publication I have and it is a technician guide published by GM Powertrain/Hydra-Matic Division.

ASE doc

Dana's Pro Built Automatics is top notch. He will spend the time with you answering questions, helping you sort out issues. Aside from putting together well thought out complete kits for your build.

For me he put together a special 3-4 clutch stack based somewhere between his road race and street strip packages. I have the Sonnax Smart Tech input housing that gives you an extra 5mm of 3-4 clutch capacity. 5mm doesn't sound like much but it allows use of 8 .077" frictions with 7 .077" steels. In fact in mine to set clearance, I ended up with 6 .077" steels and one .096" steel in the middle of the stack. That's a high torque capacity 3-4 clutch with plenty of steel for good heat dissipation. The Smart Tech also has a super rigid bolt on backing plate that pretty much eliminates coning of the clutches. I also have some other great parts, alot from Sonnax, in with the Pro Built-Transgo goodies. That makes the build more tricky to get right. Shift timing has to be adjusted to get it just right. It takes time and maybe 2 or 3 pan drops.

I have to replace the 3-4 stack again because I ignored what seemed like an occasional drag/bind on the 2-3 shift. I only noticed it at light throttle, but it was probably there at heavy throttle too. The trans just shifts so tight and quick that I didn't pick up on the bind when I was getting into the ponies. I know better than to let this stuff go. If it was a customer's car with a runnability issue, I would have burned the midnight oil to figure it out. On my car that I love and have built by hand, I let it go. Now I get to reap the rewards of being lazy.

The up side is, each time I get into this unit, I learn more. This time I really dug into the books, figuring out exactly how the hydraulics work and what the 2-3 kit does. I was just about here last time but once I got the unit working pretty close to perfect, I closed the books and back to burning rubber.

Dana uses and stands by the Transgo 2-3 kit, with his own special touches, so we know it's good stuff. I just never understood what all the changes were. The benefits of increased line pressure are obvious, but the shift strategy mods were a mystery. I love a good mystery, when I solve it. Not so much when I don't, and it's in my own car. I see now that Gil and his people really went to town reprogramming the shift controls, especially between 2nd and 3rd, where the biggest problems lie.

ASE doc

Just worked a full day before 10 am. Started an engine pull, on a 78 Ford Pinto, at end of work yesterday, pressure washing the underhood and undercar. Had the engine ready to go on the truck to the machine shop at 8AM this morning. That's working til 9 last night and starting again at 5 this morning.

Hopefully, I can get out of here early today and pick up some parts for the 700 from Perfection Plus and Portland Transmission Warehouse. The trouble is that Jerry at Perfection sell the parts so cheap it's not worth paying the shipping charges. The 3rd accum check ball capsule I'm getting from PTW. The shipping charges for each would be more than the parts cost.

OrangeBird

iTrader: (1)

Hi ASE doc , Rest assured there are still plenty of us out here following your thread , I know the silence can make it seems no ones following , but I didn't want to fill your thread with empty posts . I just figured since I had no technical data to add , I'd save the fistbump till the end .

ASE doc

Thanks Orangebird for dropping in to say hi. I hope this thread will be helpful to others in the future. I never got out of here on Friday to gather parts in Portland. Ended up with appointments in the PM. I'm going to have to take a vacation day to get up there.

Hopefully, I'll have everything here in the next month and I can get the car down to the shop on a weekend to do the work. I'll take lots of photos this time. I'll also keep this thread updated with results and any changes I make to cure shifting issues following the repair.

Rpicard21

I rebuild trannies also and all you did sounds good and I agree that it is doubtful you bitched your new plates if it was me I would check the valve body the piston that controls the 3/4 shift can get stuck it can have a tiny bit of wear and freeze in the body causing possible damage by lowering the pressure holding the third gear main piston and slowing the plates to slip , also rite in the third gear pack the main app piston has a few rubber seals if there is a crack in the rubber or a nick in the rubber ring it will cause 3 Rd not to engage . Did you replace the rubber rings in all the clutch pack Pistons and completely check the valve body for wear ? And as simple as a piece of dirt getting caught in the valve body piston that could cause third to stop working. Check your pressure if that's good drop your valve body making sure to free up all the valves and Pistons solinoids etc check the pin filters and filter for lots of crap . If it all looks good test drive it again if it still has the issue pull the trans . The 700r4 and 4l60 are my favorite trans I can make them hold 600 hp easy 800 on the outside and have built a 4L80e to hold in the 1500 hp range

Rpicard21

I rebuild trannies also and all you did sounds good and I agree that it is doubtful you bitched your new plates if it was me I would check the valve body the piston that controls the 3/4 shift can get stuck it can have a tiny bit of wear and freeze in the body causing possible damage by lowering the pressure holding the third gear main piston and slowing the plates to slip , also rite in the third gear pack the main app piston has a few rubber seals if there is a crack in the rubber or a nick in the rubber ring it will cause 3 Rd not to engage . Did you replace the rubber rings in all the clutch pack Pistons and completely check the valve body for wear ? And as simple as a piece of dirt getting caught in the valve body piston that could cause third to stop working. Check your pressure if that's good drop your valve body making sure to free up all the valves and Pistons solinoids etc check the pin filters and filter for lots of crap . If it all looks good test drive it again if it still has the issue pull the trans . The 700r4 and 4l60 are my favorite trans I can make them hold 600 hp easy 800 on the outside and have built a 4L80e to hold in the 1500 hp range , I'm sure you have a good manual for the trans you are using a .500 tv valve and a newer pump all I can think of is there was some damage to the third valve piston in the body causing issues

ASE doc

Thanks Rpicard. If you read a little further, I think I talk some more about this trans. I did have an issue the first time I assembled it with the lip seal on the 3-4 piston rolling about 1/3 the way around. This had to make for a good cross leak. That and not getting all the sep plate plugs completely flush. I still had 3rd gear, but the trans wasn't what it should have been and I did end up burning the 3-4 clutches eventually.

The last time I went through it, I did better. I also did some major upgrades. Line pressure after the last build was 285psi at 4,000rpm, full TV. The shifts were pretty much perfect, but I did have a drag between 2nd and 3rd. It was more noticeable at light throttle but I'm sure it was still there at full throttle too. The shift wis just so quick at that point, I didn't notice the drag. I always knew the drag was the big Superior servo not releasing quickly enough. If I had gone back and fixed it right away, I wouldn't be back here now talking about losing 3rd gear again. I'd still be out grabbing gears.

I have put together some new options for the 2nd servo. I do like the big Superior piece but it doesn't have cushion springs, since it's just one big circle of billet. It's also got a 1:1 apply to release side ratio. I'm pretty sure the TH400 coast clutch servo spring by itself will solve the problem. I do however have the Sonnax Superhold and a great cushion spring package ready to go in. A good friend, who's also a veteran trans builder recommends using the TH400 coast clutch spring with the Sonnax servo. I already have the Sonnax 4th servo. The two Sonnax pieces will work great together, without any mods to match them up. If I keep the Superior servo in there, I will want to do some work on it, that I should have done before, to make sure it doesn't have issues with the Sonnax 4th servo.

I will of course check the VB out again. It's got the Transgo 2-3 shift kit in it. It was in great shape when I built it. The trans only has about 6Kmi on it since the build and the fluid is perfect, not burned and no sign of friction material. I'll see what I find in the pan but I'm pretty sure that I just burned the 3-4 clutches by dragging the 2nd servo on the 2-3 shift. The one thing I'm concerned about, that I haven't prepared for, is the Sonnax apply and pressure plates that go in the Smart Tech housing. These are very special pieces and would have to come from Sonnax special order. I'm thinking they're probably fine. I may clean them up gently with some scotch brite if they are hot spotted at all.

I also manual shift almost all the time, that brings the overruns into the mix and makes the 3-4s even more likely to burn. I will take the time this go round to make sure shift timing is perfect, no drag and no flair. I am going to make some changes in the 3-4 clutch cavity, as well as replace the 3rd accum check ball with a brand new one. The changes will be to remove the Transgo high rev springs going back to the stock springs on the 3-4 and overrun pistons, and to install the Sonnax boost springs that came with the Smart Tech housing. I'll also remove the Transgo orifice plug and install the OE 3-4 clutch check ball. I plan to drill a .035 hole at the edge of the clutch cavity, as recommended by Raybestos in their Maxpak instructions to help prevent centrifugal apply.

Here are some photos of my modified servo cover, cushion spring set, and the TH400 coast clutch spring beside a stock 2nd servo spring.

ASE doc

Another photo showing the OE booster springs next to the Sonnax Smart Tech booster springs. The height difference is obvious between the two. The difference in the springs mirrors the difference in 3-4 clutch capacity between the Smart Tech and the OE housings. The Smart Tech springs are also about 30% stiffer. This is the main reason I'm going back to the OE 3-4 and overrun spring packs. I think these stiff boost springs will be plenty to prevent centrifugal apply.

ASE doc

Just found this by shear accident yesterday.

betperformance.com/proddetail.asp?prod=SV-01

These guys offer both a 2nd servo with just slightly more apply area than the Sonnax, and also a servo with the same apply area as the Superior, but that takes the cushion springs and cover. A talked with Eric yesterday and their big 2nd servo and seperator (what you would need just to do the 2nd servo) sells for $69. That's for a part that's machined from solid billet at their shop in Nevada. I'm going to get one just to check it out. If it's what I think it is, it's going into my transmission instead of either the Superior or the Sonnax. A full apply area billet servo that uses cushion springs. It's the best of both worlds.

EDIT: I seem to be having trouble with the link above. It works only once, then goes to plain text and stops linking to the website. Can still use the .com to find them though.

tpi88camaro

iTrader: (7)

I'm curious to know what you found when you took the transmission apart and if it's all back up and running.

Tinybird

i had exact same issue, speedo going bonkers too, still diag

1982Z28Modified

Just swapped it out with a spare 700R4 i had. Never looked at it.

ASE doc

I'm sorry. I just kinda left this thread floating in space. I got the trans back together shortly after my last post. It works great and no issues with the 3-4 clutch since installing the booster springs. They really are a must in the Smart Tech housing and in the later 4L60 units that were designed to use them.

I ran the car for a 13.1 quarter mile several passes, really pushing it hard both auto and manual shifting. The trans never had any issues and after a summer of hard driving the fluid looks brand new. Of course I blew the rear end into little chunks at the end of that summer. Just got the new Quick Performance 9" rear installed 2 weeks ago.

I do plan on going back into the trans soon just to clean up the 2-3 shift a little. I've done all I can to make a clean, no bind, shift with the Transgo 2-3 kit and big Sonnax servo installed. I plan to reverse part of the shift kit and restore part of the factory 2nd servo return circuits that were deleted in the shift kit.

Next summer I'll probably tear the trans clear down again and do a final beef up on it with the Sonnax input shaft and front planet, a better pump, and maybe a 5 pinion rear planet. I'll also move up to a nine stack 3-4 clutch. Then it will be ready for the new 550hp motor that's soon to come.

Pro Built Automatics

"Next summer I'll probably tear the trans clear down again and do a final beef up on it with the Sonnax input shaft and front planet, a better pump, and maybe a 5 pinion rear planet. I'll also move up to a nine stack 3-4 clutch. Then it will be ready for the new 550hp motor that's soon to come."

Pass on the input shaft, front planet, 5 pinion rear planet. These are not necessary at all. Stock pumps are fine when set up correctly. TransGo steel rings for the vanes. Larger boost valves .500" main boost valve. .296" intermediate reverse boost valve. And the 1993 PR valve. When you want to do this right, and not spend money unnecessarily, call me.

vorteciroc

I agree with Dana of Pro Built Automatics.
Especially regarding 5-pinion planets and the pump!!!

Dana has THE MOST COMPLETE packages available for both the THM700-R4 and 4L60E Transmissions!
I send DIY builders to him all the time! You won't regret it!

ASE doc

Hey Dana, You probably don't remember cause it's been a while but I have called you a few times. I got a bunch of the parts in my current trans from you. These include the Sonnax Superhold servos, I run the Sonnax Smart Tech input housing with an 8 stack 3-4 clutch. You recommend the BW high energy fictions and that's what I have. For the power level of the next motor, I'll go up to a 9 stack of the same frictions. Before I started working with you on this unit, I already had the Sonnax Line Booster kitwhich includes their .500 boost. I have the TCI HD PRV spring, a little stiffer than the Sonnax, and the .296 L/R boost valve. The last time I checked, I have 285psi at 4K rpm. I run an Edge 3,500 stall 10" converter that is very nice.

One issue we were trying to solve was a slight shift bind manual shifting from 2nd to 3rd. Typical late servo release with the big servo stack. I up sized hole G slightly and swapped the servo return spring out for a front servo spring from a TH400. I thought I still felt some bind but I swear, since getting the car back on the road after installing the sweet new QP 9" rear, I haven't felt it yet. I bought a new sep plate and plugs to redo the plate mods of the TG 2-3 kit, leaving out the hole F plug, as I've heard this nd reinstalling the checkball can solve the bind issue. But, I think I'll wait and see. If the trans continues to shift as well as it is now, I don't think I'll change anything in the shift timing.

I know you've told me that the factory hard parts are fine up to 700hp. I would just feel better having a few of the parts that take most of the abuse be a little tougher. The Sonnax HD input shaft is an easy swap for me. The purpose of the Sonnax front planet is as much to adjust the 1st and 2nd ratios slightly as it is for strength. The new rear gears switched from 3.23 to 3.70. The Sonnax Ratio change planet will bring the 1st and 2nd ratios up just a little. I know it's not necessary, but I'm pretty set on it. The rear planet I don't know. TCI was making a gorgeous 5 pinion set with a billet case but I guess they stopped doing it. I don't care that it was pricey. Dropping another $2K+ into parts for this trans is no big deal to me. Now, it looks like the only 5 pinion rear planet offering is some AM piece from PATC or the chinese junk floating around out there. Aside from cheap prices on a few good part numbers, I don't have much use for PATC and I have little faith in an AM part their pushing. So far, through a few teardowns now, my planets have held up very well to years of hard use. You helped me understand the importance of lubrication in the equation. If I have to retain the stock rear planet, so be it.

NoEmissions84TA

iTrader: (1)

Just add pdf to that search string. Like this: 700R4 Principles of Operation pdf

Here is the 1992 4L60-E manual: https://share.qclt.com/%E6%B1%BD%E8%...%20English.pdf

vorteciroc

Thank you for the Hyper-Link for the 4L60E manual. It is good to have for people doing the swap.

Do you have a link for the THM700-4R/ 4L60?

NoEmissions84TA

iTrader: (1)

You mean the link in post #16?
http://www.1990suburban.com/repair_a...nd_Edition.pdf

vorteciroc

Nice Find!
I still have physical copies of these; but digitally distributing the information is great!

That will service 1984-1986 completely, mostly 1982-1986, and partially 1982-1992.