novass

iTrader: (1)

Hey anyone ever have a situation where they get a clunk only when the trany shifts from 2-3 under normal acceleration.

The clunk is definately from the rear, and it only occurs on the 2-3 shift not any other time. If I am on it, it will not clunk.

Universal Joint?? It seems a bit odd that it only occurs when it does.

Your thoughts?

I will probably replace the universal joints first with some HD Servicable ones.

prOject-IrOc

might wanna check your torque arm bushing. when mine wore out, the car would only clunk when i was driving "nice".

then it got to where it would clunk every time i shifted to any gear.

NEOMASTERZ28

I have the same clunk but i replaced the bushin and still does it and still does it . i have a new rear end and rebiult tranny w/ shift kit so i dont know why its doning that either

novass

iTrader: (1)

I know for a fact the the torque arm bushing is fine and the clunk is definately in the back.

25thanniversZ

probably caused from the 2-3 shift hesitation as in when engaging from the 2nd gear band to the 3rd hard gear...in a since the ever so slightl hesitation you cant realy feel is alowing slack in the drive shaft then engaging in 3rd it hits because the torque arm is taking pressure again

Pro Built Automatics

If you have "too much" overlap (two gears on at once) with the 2-3 shift?, you might have this situation. C-6 & TF727's were notorious for this. What it is exactly, is the band & clutches are on both at once momentarily, this tries to stop the driveshaft, and when released, a mild snap/bang can occur in the driveline. In the 1-2 or 3-4 shift this will not happen.

novass

iTrader: (1)

Is this something to be concerned about? Or is it just more of an annoyance?

novass

iTrader: (1)

Well it is not the universals...Took them to Dennies Driveshaft Service, Some of you guys may have heard of him he has been featured and his products on many many car magazines, He said that the universals were fine and the GM way of inserting the universals is crap.
In fact the GM drive shafts after 80 were crap. He said that if the universals needed to be replaced, there was like a 50/50 chance that the shaft would wobble and that balancing may not take care of the problem.

25thanniversZ

novass summed it up pretty good

novass

iTrader: (1)

Those that are transmission experts?????

NEOMASTERZ28

so will an aluminum drive shaft should fix the problem

jimjohn

I HAD THE SAME PROBLEM WITH MY 89, JUST ABOUT DROVE ME CRAZY.
TRIED EVERYTHING, TORQUE ARM BUSHING, LOWER CONTROL ARMS AND FINALLY HAD THE TRANS REBUILT (77K MILES), NOTHING HELPED.
THE CLUNK WOULD APPEAR SOMETIMES AS I RELEASED THE BRAKES AND STARTED MOVING AND SOMETIMES WHEN DOING A SLOW TURN.
I FOUND THAT THE REAR BRAKE BACKING PLATES WERE WORN IN THE AREA WHERE THE SHOES HIT THE BACKING PLATE.
I RECENTLY REPLACED BOTH BACKING PLATES AND WHEEL CYLINDERS (WERE VERY STIFF) AND THE PROBLEM IS SOLVED.
MY 60 FT. TIMES HAVE BECOME MORE CONSISTENT, PROBABLY CAUSED BY THE BRAKES DRAGING.
HOPE THIS HELPS SOME.
JIMJOHN

avro206

I was having almost the same thing...2-3shift but under "assertive to heavy accleration" never noticed under light aclereration.

Took a few months but I lost 2nd gear and o/d and trashed my torque converter.

had the trnas rebuilt--no more noise

RBob

iTrader: (1)

If this problem occurred after the install of a TransGo shift kit is there something I can do to eliminate it? (700R4, custom kit).

The driveline snap is worse with a cold trans and is reduced as it warms up. But it is still there.

Thanks,

RBob.

RBob

iTrader: (1)

ttt

whiteminqua

The last time this happened, like 7 years ago, the tranny mount was shot. Its a cheap piece, change it out and see.... Get the stock part.

novass

iTrader: (1)

Yup this is when mine showed up. I am still hopeing that someone has an answer.

RBob

iTrader: (1)

Last night I studied a transmission manual a bit. Looks like the problem is that the 2-4 band is not being released quick enough. It is the job of the servo to hold this band applied and then release it as the 3-4 clutches apply.

I can now see why this snap/bang can only occur on the 2-3 upshift. I'm going to look at it again tonight and try to get a better idea of how to get the 2-4 band to release quicker. Can also have the 3-4 clutches apply later, but I don't think that is what we really want.

RBob.

formularpm

I am having the exact same problem as you guys, I noticed it after putting in my rebuilt 9bolt. Theres a clunk coming from the rear under normal acceleration, only on the 2-3 shift! Ive tried two different driveshafts, and all my bushings and mounts are tight. ???

RBob

iTrader: (1)

On a smooth road concentrate on how the car accelerates at each shift, 1-2 then 2-3. If the 2-3 problem is in the trans it will stop accelerating during the shift then clunk, as it accel's again.

The 1-2 shift will feel continuous. Pro-Built put it best when he used the words 'snap/bang' for the 2-3 clunk. The clunk actually being the slack in the rear being taken up after the trans binds (2 & 3 both being applied) then releases 2nd.

RBob.

novass

iTrader: (1)

Keep me updated!

Maybe we could get one of the transmission pros to chime in!!

RBob

iTrader: (1)

This 2-3 clunk seems to be a common problem. Here is another thread where the person has major snap/bang on the 2-3:

https://www.thirdgen.org/techbb2/sho...threadid=53235

If I get the chance this coming weekend the valve body will be coming out to change two hole sizes. It looks like shrinking the [edit: make that the 3rd feed, was: 2nd feed] and enlarging the 2nd release may cure it.

edited to correct spelling error. . . and edited again to correct 2nd feed to 3rd feed.

RBob.

novass

iTrader: (1)

When you do do it could you take a few pics of what you did and the new hole sizes so if you are sucessful, those of us with the problem can give it a try.

Rbob is D'a Man!

Thanks
Tom

RBob

iTrader: (1)

In an attempt to eliminate the 2-3 shift clunk I changed some items in the servo this weekend. The changes were to re-install the snap ring and remove the band adjust shim. These changes netted a significant reduction in the 2-3 snap/bang clunk-from-the-rear.

I can no longer feel the binding, however, the rear will still clunk ever so slightly. More so on a low throttle down hill shift vs. a 3/4 throttle shift on level pavement.

I made the above changes to try to get the servo to release the 2-4 band quicker. It did do that but still not quick enough.

As a reference point the servo is now set up with the 093 servo vs the 554 never use servo (stock). And has the added blue cushion spring (as Vette's have a cushion spring w/the 093 servo). So the servo setup closely resembles a stock Corvette transmssion.

Another effect of this change is that the 1-2 shift is not as quick (brutal?) as before. Previously the 1-2 shift would pull hard, like a no-lift speed shift on a stick car. The car would briefly accelerate at the 1-2 shift even at 1/3 throttle.

Even now the 1-2 shift is still positive and quick. More to come. . .

RBob.

RBob

iTrader: (1)

And now for the valve body (separator plate) changes and results. I changed four hole sizes, 3rd apply (A), 2nd release (G), 3-2 shift (C), and 4th apply (E). The 4th apply was changed as I found some info posted by Dana. His 4th apply size was larger then what I was using, so I changed it. I changed the 3-2 shift feed to reduce how brutal that manual shift is.

To eliminate the 2-3 upshift clunk, snap/bang I reduced the 3rd apply and increased the 2nd release. Here are the current hole sizes (all):

A: .155 (3rd apply, from .173)
B: .089 (2nd apply & stock GM size)
C: .146 (3-2 downshift, from .169)
E: .185 (4th apply, from .175)
G: .116 (2nd release, from .113)

The results: very much improved. Dependent upon the throttle position and engine load there is either no noise at all or just a very slight 'clink'. This is much better then it was previously. Note my post right before this one where I also made changes to the servo (5 days ago).

I haven't tested the manual 3-2 downshift, I am almost afraid too as it had been so brutal with the original hole sizes. And 4th applies just fine-n-dandy.

I'd like to make some further adjustments but for the effort involved in dropping the valve body I don't think I'm all that anxious to do it (actually I know that I am not all that anxious).

If anyone else would like to add some info/ideas/tips am I all ears (or in this case all eyes ).

RBob.

P.S. Note that the vehicle/trans is a 1992 with the 4L60. I installed a TransGo reprogramming kit with the accumulation setup. It was at this point in time that the 2-3 upshift clunk started.

Upon rebulding the rear and changing from a locker to a Torsen differential the 2-3 upshift clunk/bind/snap was worse. With the Torsen it became obvious that the transmission was binding on the 2-3 upshift.

novass

iTrader: (1)

thanks for the info Rbob. Once I finish painting the car and get a chance I think I will dive into it.

Thanks for all of the info on sizes of holes!

RBob

iTrader: (1)

Ack, sometimes things just aren't what they seem to be. I now do not believe that the spacer plate hole size changes made any difference. I re-adjusted the TV cable and it is the same as before the hole size changes.

The change to the 2/4 servo DOES make a difference.

It was late once I got the valve body back up and finished up. So a quick test drive then drove the car to work the next day (Friday). Then posted.

Noticed that the part throttle shifts were a little early and made a two-click adjustment on the TV. Bam, back to the light clunk on the 2-3 shift (lots of driving on Sat).

What is interesting is that TransGo hijacks the 3-2 control valve and turns it into a 1/2 control valve. I always wondered why the new 3-2 control valve was sooo different then the original. This is done in conjection with blocking hole 5 and drilling the vent hole (F) through the bottom of the valve body.

The original 3-2 control valve is also part of the 3rd accumulator oil feed.

In my studies I've also discovered that the 3rd accumulator oil (which releases the 2/4 band) has to work against the 2nd apply oil. This is all in the servo. When the trans shifts into 2nd the 2nd apply oil forces the 2/4 band to engage.

When the trans shifts to 3rd, this 2nd apply oil is still present, so it is the job of the 3rd accumulator oil and the servo return spring (the one on the pin, first to into the servo bore) to disengage the 2/4 band.

Why is this important? Because when you upgrade to the 'Vette servo there is more 2nd apply area. This in turn will make it more difficult for the 3rd accumulator oil to disengage the 2/4 band.

Bind/snap/bang anyone? It just may be contributing to this problem. If I understand all of this correctly then hole 'G', 2nd release, is really the 3rd accumulator feed.

Back to the snail-trails. . .

RBob.

RBob

iTrader: (1)

Now I know why changing the hole sizes didn't change much: hole A (3rd apply) directs the oil from the manual valve (now RND4 D3 oil) to the 2-3 shift valve. Changing this hole size affects both the 3rd clutch and 3rd accumulator. Not what I intended.

With some research today I also discovered that the 3rd accumulator check ball capsule likes to leak. If leaking this will cause the 2nd release to occur later and contribute to the 2-3 snap/bang shift. Apparently some/alot of rebuilders replace it with a cup plug. Others will place a Sonnax part behind the current one. Does anyone have any input on which is the best way to go?

Unfortunately this means dropping the valve body to make the change(s). Although I am getting better at it, LOL. Problem is, I don't want to drive the car until this is fixed. I installed a TransGo to increase the longevity of the transmission, not decrease it.

I am also making an effort to see if the 'vette servo uses a different servo return spring then the 553/554 servos use.

RBob.

RBob

iTrader: (1)

Made another change: swapped the 093 servo for a 553 servo. This is still an upgrade from the stock 554 servo. Results: much, much better, but not perfect.

The servo has the added cushion spring and the snap ring is in place. I am going to drive the car like this for a while. Maybe some day I'll do something with the 3rd accumulator checkball capsule. At this point in time this is where I believe the problem really is.

(Note: the following 3-2 testing was done with the 093 servo). As I mentioned before a manual 3-2 downshift is brutal. I did some testing (at low speeds!!) and it feels like there is again a binding with the 3/4 clutches and the 2/4 band. It is the opposite where is the 2/4 band is being applied before the 3/4 clutches are released.

A 3-2 manual shift causes the rear tires to screech on the pavement. Then suddenly release. Again, a 2/4 band, 3/4 clutch timing problem.
(Note: have not yet tested the 3-2 manual shift with the 553 servo).

From web searches there is a lot of talk about replacing, reseating, bypassing, or adding to the 3rd accumulator checkball assembly. In hindsight I should have at the minimum cleaned it and reseated the ball when I had both the servo and valve body out. Or, just replaced the darn thing.

The valve body needs to come off in order to R&R the 3rd accumulator capsule. Doesn't look like an easy job to replace it with the trans in the vehicle. But it can be done.

RBob.

RBob

iTrader: (1)

Dragging this post kicking and screaming back to the top. . .

Trans is apart again, 3rd accumulator checkball capsule is out. Now it's time to make a decision. The game plan was to inspect the 3rd accum checkball capsule and if there was a problem with it to just replace it (3rd accum checkball capsule is in the servo bore area).

If there didn't seem to be any problem with the checkball capsule then I was going to plug the top of the passage. This is something that many shops do. Using a cup plug and driving it to the top of the bore.

Not sure now, and this is why. Further study shows that the TransGo kit plugs a check ball hole in the separator plate and enlarges the orifice next to it. These two orifices are in parallel (G & F). Disabling the one makes the other do all the work.

So what does this do? Stock, both orifice pass fluid on the 2-3 shift (upshift) which is what pushes the 2/4 band off and provides accumulation for the 3/4 clutch pack. The more fluid the faster the band comes off and the slower the 3/4 clutch packs apply.

On a 3-2 shift (downshift) the checkballed orifice blocks off. The parallel orifice flows regulating the time it takes for the 2/4 band to (re)apply.

Now, the checkballed orifice is .210", while the parallel orifice is .064". The transGo kit only has the parallel orifice at .110 to .116" (F is plugged).

So, with this in mind. . . on a 2-3 shift the 2/4 band is now slower to release. And, on a 3-2 shift the 2/4 band is quicker to apply. Hmmm, fits with the problems I am having. A bind/clunk on the 2-3 upshift, and a brutal bind tire screeching 3-2 manual downshift (even at low speeds).

Seems to me the real answer is to remove plug F, shrink hole G down and use the check ball.

Am I on the right track?

RBob.

RBob

iTrader: (1)

Last night a friend and I were discussing what I had discovered concerning the blocked checkball'd location in the spacer plate. Then it hit me like a ton-of-bricks. . . I am on the right track about having the checkballed location (hole F) blocked off. There is a major difference between high end re-programming kit and the Jr Shift kit.

I'm not going to say what it is right yet. Not until I try it out. As it is I have new gaskets, filter, 3 accum checkball capsule, and spacer plate (GM calls it a spacer plate, I've always thought it was the separator plate). Note that the 3rd accum checkball capsule is a different checkball then the one that is blocked on the spacer plate (hole F).

So, I am going to install the new 3rd accum checkball capsule, and update the new spacer plate by blocking two holes and leaving hole F open. Then drill out the other required holes.

Oh, and a drain plug. Everyone says to do it the first time the pan is down, but, no, not me, I wait until the fourth time the pan is down. . .

Once back together I'll update on how it works out.

RBob.

novass

iTrader: (1)

I am still hanging on you every word RBob

91dubZ28

I had that problem it was more of a slight grind. When i was just normaly accelerating it would do it but if I was racing or getting on it, it would be fine. Then my tranny went, so I dont know if it was that or not, we will see when I get the t-5 in there. ohh and I have a new rear in there with all new bushings too...

rleprechaun

Don't forget to check the trans mount before you go into the transmission. Mine was worn out and it caused the exact problem you are discribing.

RBob

iTrader: (1)

You read it right, no 2-3 upshift clunk, the clunk is gone. As a secondary improvement a manual 3-2 downshift now works correctly, no more binding (I held my breath and grit the teeth as I tested this shift). First, what changes I made, then the theory.

I replaced the 3rd accum check ball capsule.

(Note: all hole designators are for the re-programming kit).

Starting with a new spacer plate I plugged two holes: D & 5. I left hole F open. Holes D & 5 are used in conjuction with the new 1-2 upshift valve, and still need to be plugged.

As for the drilled out holes I used the hole sizes as found in the Jr Shift kit. A: .110, B: .089 (stk), C: .110, E: .110, G: .076 (hole letters as in the re-programming kit). The idea was that I can always make them larger down the road.

All check ***** were used same as stock setup.

The servo is still setup as previous, 553 servo, snap ring in place, added cushion spring. (I may change to the 093 servo and/or remove the snap ring. May even shim the cushion springs a bit. This is soemthing I'll do after additional testing.)

The big change was leaving hole F open. This install of the TransGo kit is a combination of the re-programming kit and the Jr Shift kit. The big difference is in how the 2/4 servo 3rd accumulator stackup is modified.

With the Jr kit the 3rd accumulator is modified by adding another cushion spring and leaving the snap ring off. Hole F on the spacer plate is left open while the 2rd release orfice (hole G) is enlarged a tad (holes F & G are in parallel with a checkball on hole F).

With the re-programming kit the 3rd accumulator is stacked solid with washers. Hole F is plugged while the 2rd release orifice (hole G) is enlarged quite a bit (but still not as large as hole F that was plugged).

With the combined kits the 3rd accumulator is modified by adding another cushion spring and leaving the snap ring off. Hole F on the spacer plate is plugged while the 2rd release orifice (hole G) is enlarged.

What happens when the two are combined in this manner is that the cushioned 3rd accumulator comes off too late. Hole F is plugged and hole G isn't large enough to flow the required oil. Snap bang bind.

By opening hole F again there is now enough oil to push the 2/4 band off quickly enough via the 3rd accumulator. Another fix would have been to stack the 3rd accumulator solid with washers and leave hole F plugged. I wanted the accumulation and went the other route. The servo stacking would be an easier/quicker fix.

Getting a clean 2-3 shift is all in the timing. The 2/4 band needs to be pushed off while the 3/4 clutch pack is applied. If there is not enough overlap a flair occurs, too much overlap and a bind occurs.

Here are some GM part numbers:

Spacer Plate 'CS': #8673441
Spacer Plate gaskets: #8689949
3rd accum check ball capsule (in servo): #863440

Note that each part was $6.18US, strange but true.

They are for a '92 4L60.

RBob.

RBob

iTrader: (1)

Heh-heh, had a chance to drive the car again. . .and. . .and.. still no 2-3 clunk. This definitely fixed the problem. And it shifts decently. Firm with quick shifts.

A little more info. These are what each hole function is:

A: .110 3rd feed (both 3/4 clutches & 3rd accum)
B: .089 2nd feed (stock)
C: .110 3-2 downshift
E: .110 4th feed
G: .076 2nd release (F also: .210 stock)

Note: holes sizes per Jr kit, hole designators per Re-programming kit. As such some holes may be made larger with no effect on the 2-3 shift.

RBob.

novass

iTrader: (1)

Thanks Rbob for all of you hard work and documentation :yourock: , now I just have to find the time to do it!

novass

iTrader: (1)

Are you sure about this # I cant seem to locate it on GM parts direct

3rd accum check ball capsule (in servo): #863440

RBob

iTrader: (1)

Ah yes, I dropped a digit: a zero from the end.

#8634400 retainer

-or-

#863-4400 valve

Same number, two different descriptions. Both on the same package.

RBob.

novass

iTrader: (1)

RBob,

What did you use to plug the holes? I do not have any more plugs from the original transgo kit.

I have ordered the parts and will give it a try soon!

RBob

iTrader: (1)

For the smaller hole I used a hard solder. It is the newer lead free plumbers solder. Cut a small piece off and flattened it into the hole. Something like Stay Brite would also work (has some silver in it as do some of the lead free solders).

For the larger square hole I used one of the left over TransGo plugs. Had to trim the plug with wire cutters before installing. If you can get some dead soft aluminum that will work (that is what the transgo plugs are).

RBob.

rleprechaun

Have you guys ever considered that you set the band up too tight. The Delta automotive kit that I use says the band must be floppy loose. I just put a full Trans-Go shift kit in my 700R4. Installed it as per the Trans- Go instructions and had no 2-3 shift problems. Put the car up in the air with the wheels off the ground. With the transmission in neutral the driveshaft should turn freely. If there is ANY friction from the transmision the band is too tight.

novass

iTrader: (1)

Yep! Been there done that!

novass

iTrader: (1)

Rbob
Why did you repalce the:
?

There weren't any changes to that with the transgo kit.
How did you get to it? Thru the servo opening?


Thanks
Tom

RBob

iTrader: (1)

I replaced it as they are apparently troublesome. A slight leakage and the 2/4 band won't get pushed off quickly. Many shops remove and then cup plug the end of the bore. In order to R&R it you need to come up from the bottom under the valve body. IE: remove VB and pull it out from the passageway in the case.

Here is a thread where I described how I removed it:

https://www.thirdgen.org/techbb2/sho...hreadid=200257

Use a 3/8" rod to insert new capsule 42mm from face of case.

RBob.

novass

iTrader: (1)

Well I did some changes, but still snap bang.... I drilled out the F plug in the original plate ... snap bang.. I figured well I'll take .060 off of the servo pin, (this way if i take off too much I can just put in the shim that came with the kit).. snap bang..

Well when I get the chance I will try the new plate and check ball assembly...

ASE doc

Old thread, Good information. Subscribed.

ASE doc

Getting ready to go through this process myself. Just got my new separator plate. I have the Transgo 2-3 kit installed along with the Sonnax 2nd and 4th servos. I installed a TH400 servo return spring, quite a bit stiffer than the 700 spring, that helped some. I still feel a slight bind manual shifting from 2nd to 3rd. I figure that going back to the Jr. shift kit 2-3 shift mods should work well with the big servo.

I'm also thinking about swapping back to the stock servo spring. My concern is that with the original 3rd accumulator/2nd servo return fluid circuits restored, the big spring may cause the servo to return too quickly, causing a flair. I can always do the sep plate first, then do the spring later if needed.

sofakingdom

iTrader: (1)

That's a hard shift to get right. It involves one clutch device (the band) letting go, and another (3-4 clutch) applying.

If it's not perfect, you either get the "flare" in between gears, or you get "overlap", where the transmission is effectively in 2 gears at the same time, and is actually acting like a brake on the rear wheels. Overlap, a SLIGHT amount, is preferable. Too much is what causes the "clunk" when the transmission goes from driving the rear end, to being a giant drag on it, then back. Whatever backlash there is in the drive train gets fully exercised.

ASE doc

Mine isn't that bad now. I just don't want to tear up my 3-4 clutches by having the double apply when I manual shift from 2nd to 3rd at 6K. It will be more of an issue now with the 3.70 rear gears. The governor will shift way too early. I should really work on my governor shift points so I don't need to manual shift. But that's almost as hard as getting the 2-3 shift right.

I'm going back through the worm tracks to be sure of what the change will be. In the 2-3 shift kit we eliminate the 3-2 shift control valve and block off some of those circuits. I want to try to get hole F close to the right size for the big servo. I don't look forward to going through this process numerous times.