I tried finding some threads that maybe would’ve talked about this but they ended up all being about the great lockup “hunting” debate so hence this thread. At what throttle position should I expect the 4-3 downshift to be given I’m going 55-65 mph? I have a 2.73 rear as of current and it seems to be at around 1/3 throttle, is that okay? Seems a little high to me sometimes, my trans is from a formula 350 car and seems to have a higher stall speed in it so it makes it feel very sloppy and weird when on the highway without lockup.


btw for those who are inevitably gonna yell at me for not running lockup I bought a painless kit and I’m waiting till I have space to install it.

 

There a several variables that control the the shift points. Downshift included.
First and foremost is the proper adjustment of the TV cable. It has a direct influence on shift points and as you probably know, it's installed geometry is critical to achieving proper line pressure. Mis-adjustment could soon destroy the transmission.
Next up is the governor. They're vehicle specific in that there are several different models designed for different applications and /or cars. A F-body with a low numerical rear gear and a V6 would have a different governor than a 305 with a higher numerical gear.
While this isn't necessarily the cause of the issue you're describing, there's a thread to the governor workings. The detail begin at post #22.

https://www.thirdgen.org/forums/tran...s-springs.html

While you might have a decent guess on the history of the transmission, after 40 years of service, any number of modifications or substitutions could have been made.
These are starting points with the TV cable front and centre.
I will ask though:

What do you mean by "a little high"?

 

a little high meaning the throttle input it takes to activate the passing gear at highway speeds, lets say im going 40 and I want to pass someone, the passing gear (4-3) shift is almost instant at 1/5 throttle, however getting to highway speeds 60+ it seems like I need to press the throttle a lot more to command that same passing gear shift.

 

I've witnessed that occurrence under a couple of conditions. The first one was the result of a misset TV cable. RPMs were unreasonably high before a shift would occur. The other came about as a result of a transmission swap. I had a transmission from a 90 Caprice and the governor characteristics didn't match the drivetrain of the Camaro it got installed in. That's why that thread on "tuning" the governor came in so handy. That said, rather than tuning, I had the original core still and swapped out the bits needed.
There could be other issues most definitely, but those are two that I've had to deal with myself.

 

My governor has definitely been messed with in the past to get higher WOT shifts (admittedly higher than I like) around 5500, my part throttle shifts at times seems early but my old tranny was pretty good, I’m gonna try and track my old tranny down to see if I can rob the governor off of it. I verified the TV adjustment with my friend in the car and the pan off today while I was installing the painless performance lockup kit, it’s definitely correct.

 

If you check out that thread about the governor, you'll find that you can manipulate part and WOT shift RPMs.
As for the TV cable adjustment, great.
As I said though, there could be other root conditions giving you the symptoms you're describing.

 

this is what I found in the pan last night, those black particles were almost like hard plastic and they were very chalky, I’m assuming that’s not good lol, probably friction material. I think my torque converter is failing to some degree as well because for a stock stall it feels way too loose and it locks up very slowly. Maybe I’ll have a shop look at it and see if a rebuild is imminent.

 

That's pretty chunky looking debris. Difficult to assess from this side of the keyboard however, while you may be able to put it back into service, any signs of slippage put you a path for a rebuild.
Is the filter also full of this stuff?
Remember too that any rebuild will mean a new converter. Or at the very least, cutting open the one you have for a thorough cleaning and an examination of the TC clutch. Don't forget to blow out the lines and (if equipped) the cooler as well.

 

The filter surprisingly looked clean minus two or three of those tiny little particles which is very weird to me. No gears are slipping at the moment and the shift changes are very quick, hopefully it remains that way. If I’m in 4th and I bypass the vacuum switch so it stays locked no matter what throttle input I do notice the RPMs rising if I get into the throttle but I’m pretty sure that’s just the torque converter clutch slipping which leads me to think converter needs replaced, if I disable the lockup entirely and get into the throttle in 4th it loads the way it’s supposed to with no slip.

 

Remember that the TCC in these OEM converters aren't designed for much more than cruising in O.D.. That's where, as you obviously know, the vacuum switch comes in. I had, at one time, incorporated an adjustable switch so I could change the set point but ultimately I went back to the OEM version as it seemed to work the best. Something I may revisit seeing as I've got a new powertrain and the engine, transmission and converter characteristics are very different from the previous iteration.
I've wired in an option where I can have lock-up in third but even though I've an aftermarket converter, it's still a single disc and hasn't got the higher holding capacity of the triple disc option that, in retrospect, I should have gone for. I'm not entirely certain how some people will chassis dyno their 4L60 equipped cars with the lockup in third. I'd be afraid of shredding mine.

 

I had the pan off and noticed the TV plunger bracket that pushes it down is bent out of shape causing weirdness to happen mid throttle, that's probably what it was, I band aided it for now and the trans still feels less like a slushbox at mid throttle for what it's worth. I'm gonna be replacing the assembly with the one from my core transmission soon when I get access to the lift again.

 

That's an odd one but at least you may have found something. Slushbox notwithstanding!

 

How is everything going now?


 

The "z bar" is what's bent I think, I have a 1991 4l60 core from a thirdgen with a transgo kit that lost 3-4 due to someone messing with the governor that I want to get rebuilt. I'm hoping its cheaper to bring it to the shop than the 2,000 - 3,000 I was quoted for R&R. This tranny feels like a slopfest driving around, I cringe everytime I pass someone because I feel like it's about to break. the 3-4 shift at highway speeds feels like I'm in limbo.

 

That "slopfest" and the crap in the pan are probably related.
In my experience, the first thing to fail in it's entirety is the 3/4 clutch pack. Suddenly, you have extra neutrals!

FTR. I paid $4k for my rebuild and that with a boatload of Sonnax and new GM parts hard parts that I salvaged from the failed build before.
Plus $1100 for a converter.
But, as the saying goes, if you want to play, you have to pay.

 

I've been noticing my part throttle 1-2 shift getting softer and softer as the months go by, very exciting! Most suspensful transmission ever.

I only need mine to hold up behind 300 horse or so. So maybe it will not be as much to get that 4l60 rebuilt but who knows what they find, vette servo and the sonnax 4th super hold are a must though when I do actually get it done.

 

You know what man I give up trying to understand this transmission…. Now all the sudden it’s GOOD????, I put a new "Z bar" in and it feels like a good transmission again, it was just flopping against the TV linkage.

 

Don't you just love transmissions?!
Maybe, and I'm guessing, is that with new fluid and a filter, plus the TV adjustment, that you're making good line pressure. No potentially clogged filter either. You may earned yourself a reprieve!
Or tomorrow it craps itself. Who knows? But good luck just the same. Best case is that you've bought yourself enough time not to have source and fund a rebuild in a rush. It can be cheaper and easier that way.

 

The Throttle Valve plunger sleeve has has a two hole part throttle 4-3 downshift passage in the aluminum plunger sleeve. There four different versions (that I am aware of) of where the position of these holes are in relation to the plunger is going to determine a 4-3 downshift when giving it a lot of throttle. If these part throttle holes are closer to being uncovered, (when pushing in the steel plunger) then it takes less throttle to make a 4-3 downshift. When the holes are further away. The more throttle, it takes to uncover these holes to allow a 4-3 downshift. If you want to know which one you have. You have to look at the tip of the aluminum TV plunger sleeve. For example when you push the steel plunger in with your finger. As soon as you make contact with your finger touching the aluminum sleeve. Look at the area where your finger made contact. If you see the number 2 or two lines. You have the earliest and easiest 4-3 downshift. If yours has a number 4 or four lines. This takes more throttle to uncover these holes for a 4-3 downshift. If you have a number 5 or five lines. This takes even more throttle to uncover these holes for a 4-3 downshift. The last one is the 1991-1993 Higher Horsepower Corvette (rare to find these). I do not remember the ID number on these. However, the 4-3 holes do not exist on this TV plunger sleeve. This is the only on available from the factory to allow WOT at high speeds in 4th gear without it going back to third gear. In almost of my modified TransGo Shift kits I add two small Allen screws along with instructions to be added to any sleeve to allow you to hold 4th gear at WOT without it making a 4-3 downshift.
The number 2 is good for motors with little bottom end torque 283 - 327 ci. motor. The 350 ci. and some 383 ci. motors depending on what is done to it, like a number 4. Number 5 is somewhat rare, is good for a strong 383 ci. - 406 ci. motor where you have to go to almost WOT to get a 4-3 downshift.

 

Where does the "B4C" option fit into all of this? If I understand this correctly, TransGo describes it as the 3-4 Throttle-Valve and sleeve assembly.

Further to that, what's your take on WOT in O.D? Can this accomplished with the converter locked (providing it's a triple disc and not the standard issue single)? I hear and read that it can be but there are certain mods needed internally to keep it all together.

 

If you want to make a 3-4 WOT shift and have it live! You need the Sonnax 4th apply servo. The extra wide Carbonite band. New reverse input drum, or a drum that has been machined flat. Block the 4th accumulator. Drill the 4th apply feed hole on the separator plate to .204". I would not lock the torque converter clutch in third until you make the 3-4 shift. This will keep everything alive.
I have not seen evidence that the B4C option from TransGo does much here. The 4-3 part throttle holes in the TV plunger sleeve is what determines when the 4-3 downshift occurs. Eliminating the 4-3 downshift holes will in the vast majority of cases allow you to make a 3-4 WOT shift at when the governor controlled rpm 3-4 shift occurs, or anything above governor controlled rpm shift point occurs.

 

I was exploring this at LS1Tech and came to the realization that I'm close but no cigar.
https://ls1tech.com/forums/automatic...l#post20540053
Your reply reaffirms that.
I have the 4th gear Sonnax super servo, the wide band and a new drum. What I can't comment on, as this was built for me twice (the first one ate itself up without any racing action) are the modifications to the oil control. Not sure if that can be done after the fact.
There were other discouraging remarks too in that 4th gear WOT and the clutch engaged takes a lot out the demand for oil. Nothing something I'm willing to risk. At least not at this time as the open road events are off the table for the moment and it'll be the dragstrip where I continue the car development.
Thanks for the reply Dana. Much appreciated.

 

Once your into overdrive at WOT you're already going about 120mph or so depending on what rear you have. It would almost be like going wide open through 5th gear with a T-5, when I tried this in my old car the engine RPMs are relatively low given how fast you are going and the engine struggles to overcome the aerodynamics of the car, wouldn't the torque converter unlocked be beneficial to high speed acceleration given how you can keep the engine higher in the torqueband and achive a greater top speed? Same applies to a 3rd pull on a dyno, I think the torque converter being unlocked would help multiply torque just a tiny bit more, who knows though I'm no expert and there's always exceptions that I may not be aware of.

 

My concern is what happens in an open road event where in my class, I'm allowed a 140 MPH top speed. Average over the course is (I think) 110-120. At 140, that's around 5000 RPM in 4th give or take depending on the converter slip. At it's the slip that concerns me. Slip equals heat and I've zero interest in toasting another transmission! FTR, I've been 140 in O.D. albeit for a short stretch so the power and aerodynamics play nice.
You do have a point about the converter continuing to do it's thing when unlocked. And having it locked at WOT is another matter altogether given the remarks that Pro Built made as well as several transmission people I've discussed this with.

 

140 in overdrive does sound fun, maybe one day I'll have my trans built to do that just to say it can do it and live, but for right now the way it is, is plenty fine for me. I generally leave my gear selector in D when driving spiritedly (I heard that's better for holding power than leaving it in OD?) to prevent my trans from shifting into OD altogether, mainly as a safety precaution to prevent constant upshifts/downshifts at higher speeds. with my 2.73 gearset I'm barely turning the motor at high speeds, when I put my 3.23 gearset in, it'll be 120 or so mph at 5000 RPM if I remember correctly which seems good enough for me as it is even without overdrive WOT capability given I do not race the car.


I've made a habit to move the selector to D from OD when I'm gonna mess around or do a pull from a stop, I was told it's better for the life of the trans because it shifts harder (mainly 1-2) and has more holding power in D as compared to OD. Not sure if that's actually really doing anything though.

 

I'm much the same regarding gear selection. I almost always manually shift mostly because I like to but I also get to stay at a given RPM. I prefer to be into the rev range a little so I'm no working the converter too hard (there's that heat thing again). O.D. is generally selected only when there's some steady highway cruising involved. With my tires and gearing at 60 MPH, 3rd gear with the converter locked sees 3000 RPM. In OD, it's 2000. Highways around here are 70 MPH. everybody does 75 and that's a sweet spot for my engine. 2500 isn't lugging due to the cam and it isn't zinging too high either.
All of this is new for this season as there was minimal testing last fall, so there'll be some driving style adjustment needed quite probably.

FTR: That 140 MPH (5000 RPM, 4th gear, unlocked) blast was done with a not so heavily modified transmission. All mods were done in the car (although on subsequent rebuilds it was on a bench). A TransGo 700-2&3 kit, .500" and .300" boost valves, Corvette servo and a quality cooler were about it. I couldn't kill that transmission despite the abuse it took. Ultimately took it apart because I though I had killed it but found that I had cleaned off all of the input splines in the converter. Top of 1st gear at 6200, manually shift to 2nd and BANG! That was a bit of a bummer.

 

welp, rebuild is imminent. 3rd gear WOT pulls result in a slight slip, RPM's start to run away them come back, then start to run away again. Give it up for 80,000 miles on a stock build, gotta love a 700

also found a 3.27 9 bolt rear with disc brakes for cheap that's going in.