1999Z28

So long story short.

Put aftermarket 3500 converter in, ran good, had it tuned. Had about 20 track passes and 500 or so miles on it. Felt a vibration so had it replaced to possibly cure vibration issues. While it was out had transmission rebuilt, was working properly before, with about $1300 in parts from transmissioncenter(all the good stuff).

So anyways got a new aftermarket converter, put it in, now after rebuild the new converter felt extremely loose and car would not shift at WOT into 3rd gear or 4th. 1-2 shift was fine.

So pulled it back out and had it gone through again, couldn't find anything wrong. Replaced overrun and 3-4 clutches. Same thing happened again. So after only 1 mile of driving hoping there was not too much harm put the stock converter in and it ran fine. (thinking this whole time it's a converter issue) Shifted fine/drove fine/no problems. Except about 1000 miles later it started bearly slipping into OD on easy driving. So pulled it back out and had it gone through again. The hardened input shaft was replaced with the stock one maybe thinking it was the problem, and 3-4clutches again.
So I now drove it for about a year, about 3-4000 miles with no issues. Shifts perfect, tons of WOT passes.

Took the car out tonight and immediatedly lost 3rd and 4th gear again. 1st and 2nd are still fine. 3-4 are totally gone.

So now obviously I know it's not a converter issue. The fluid kept smelling burnt, but I didn't know if it was just from the maybe 1 qt that I couldn't get out of the stock converter. Anyone have suggestions to as what could be slowly causing my 3-4 clutches to burn up or as to why only with the larger converter it burns them up immediately.

I can't name all the parts put in the tranny at the rebuild but obviously something is not right.
Is this a common used part?
https://transmichigan.com/catalog/pr...products_id=50
I had one person question it.
Thanks for any help

fasttagurl

iTrader: (12)

Are these upgraded clutches and what about your sprags? Seems like your clutches are burning up. Not a trans. expert, but this happened to me, then we upgraded to Kevlar, which did great and now we are trying a different "race only" brand. Your builder needs to give you more info. about what "upgraded" parts he's putting in your trans., because the same mistake is being made over and over.

performabuilt

iTrader: (25)

Well the ;larger converter applies more torque so could speed the demise, But Im thinking you have either a band overlap issue or a presure leakage issue. I doubt its the clutches themselves.
As for the check valve by sonnax I havent used it so I do not know about its effect on long term durabilty, I do know its very important to get the 2-4 band off quickly to avoid overlap or the 3-4 clutch will die quickly , Each builder has a different way of working to assure that But I think all will agree its very important and overlap does seem likley the cause in your case.

1999Z28

thank you so far.
They were upgraded clutches, red alto the first time, but the 2nd and 3rd they were just stock ones I beleive, bc that would've been 80 bucks each time, and I was hesistant.

performabuilt

iTrader: (25)

It sounds like you have and hydraulic issue with the 3-4 clutch. Thats being repeated and not corrected each time which is why the reoccuring failure.

1999Z28

Yeah, I talked to a local transmission shop that we usually use and have good reusults from. It's going there today, tranny's out.

They said the leaking pressure on the 3-4 clutches was probably the issue too.

The car was in there air, and checked the pressure before it got taken out.

park 75psi at idle
120-160 reving around 2k
nuetral was the same

reverse 220 at idle

manual first it had 65 just idling
then 160psi around 2000rpms

manual 2nd had 160psi around 2000rpms

It did grab 3rd gear in the air with no load on it and around 2000rpms is was only 70psi.

Didn't go fast enough to hit OD in the air.

I don't know what is normal for each gear, I know reverse is supposed to be high. The lower psi in 3rd seemed odd. But I was getting the results for the tranny shop, they wanted to know.

brake torquing in the air to about 1200 rpms in manual first was around 150-155psi.

The transmission is out, so I can't test anymore. I'm probably going to have my hardened input shaft put back in bc now its just a $295 paperweight til it goes back in. It was removed thinking it could've been the problem on the last rebuild. But I'm sure this shop will check it. The fluid is obvisously smoked.

I'll get some results up when its apart. If they can't find anything wrong either I guess my option is to just have the input drum put back to stock parts? unless it's in the valve body.

1999Z28

well, so far the only update is that the input drum broke at the top.

Now my hardened one is going back in knowing it was never the problem.
hopefully I have some luck, I'll update when it's in the car with the new yank 3600

performabuilt

iTrader: (25)

Good luck and keep us posted

Gilbert@Ace Racing

When you say the input drum broke at the top... specifically where did it fail?

The reason I ask is there may be a fix for it. We, and several other builders utilize a sleeved input drum. Whereby a steel sleeve is placed around the hub that keeps it from expanding, which could cause a pressure leak at best and a frcture at worst.

It could have been cracked during the removal and installation of the input shaft previously as well.

Good Luck.

g

1999Z28

It broke at the top where the top snap ring is. I already have a hardened one I purchased but it was taken out bc we thought it was part of my problem.

The hardened one has that sleeve in the middle of it already. Thanks

performabuilt

iTrader: (25)

So it broke the 3-4 cutch snap ring out of the drum ? This could happen due to excessive 3-4 clutch clearance and or line presure to high.

Gilbert@Ace Racing

Right.... that's what I was trying to get at. If the drum broke at the snap ring landing that could easily be related to the original issues.

Have your builder take a look at the feed holes in the valve body plate. I will bet the 3rd feed hole is too large... just an observation based on info presented though. Those snap rings do not ordinarilly blow out.

Good info. thanks for getting back to us.

g

1999Z28

The hole in the plate for the check valve (here) https://transmichigan.com/catalog/pr...products_id=50

was drilled out to match it like the instructions said. I thought one more was, but I just watched/helped the builder at the time, so I could be wrong, I'll ask the shop about it when I take the overrun piston and spring that I needed for that hardend input drum(With the sleeve), the ones I had I guess got misplaced so I have to wait on them to come.

1999Z28

I was told that by another person to.

1999Z28

I guess a quick update. The transmission is back from the builder. Only thing found wrong was that the drum broke, so it's back together with my hardened one. UPS says my yank converter will be here monday. So I'll get it in as soon as the converter shows up so I can get to the track on tuesday and wednesday.

I still can't figure out the vibration. It really almost seems to be gone now with the transmission out. I have the prothane motor mounts here now..but don't see why that would do anything really.

It was a stock flexplate and converter. And obviously the flexplate is still attached in order to start the car.

Has anyone ever seen something inside a transmission cause a vibration. Who knows, if I had a spare tranny i'd stick it on just to eliminate the transmission.

I'll get updates after it's running in a few days.

performabuilt

iTrader: (25)

A vibration fom inside the trans while not impossible is very unlikley. However the poly mounts are well known for transfering vibration.

1999Z28

It has the stock mounts in now though. Who knows, it is quite annoying though. We'll see.

Gilbert@Ace Racing

Can the vibration be felt at idle or is it while driving?

I did not see much info about it in the thread, maybe I missed it.

g

1999Z28

The vibration can be felt during driving too. Especially if you manually go to 3rd around 50 mph, about 3000 rpms, and just keep a constant speed. Or on decel the vibration is there too.

If you're cruising around 60 or so you can feel it slightly, it's always there. Then I can throw it in nuetral and it goes away.

Gilbert@Ace Racing

But does it do it at idle.

The reason I asked this was to determine whether we should concern ourselves with the pinion angle or not. I believe we should based on your last answer.

Check and verify that the pinion angle is correct. Also, check the torque arm to ensure that it is attached properly.

g