6L90 gone bad,,

[kj217]

hi all,,

i need your help and feedback,,

it all started since i rebuilt my 6L90,, only replaced clutch packs (alto for 4-5-6 and 3-5-R),, pistons,, seals and filter,,
i tuned it as per the tuning school guide and tuned stock TC to never lock,, TM was only reduced wisely,,

trans was just fine except for that ,when cold and in the very beginning of a drive, it bucks few times,, it does it in current gear no shifting involved,, by bucking i mean locking (like instant P) the drive train for an unknown reason,, i didn't care enough since it only happens once cold or started the engine on an incline,,

last night,, i pulled WOT running from 3rd up to 5th where drive train disengaged completely,, engine can rev freely,, i pulled over and started over again,, car moved in 1st 2nd and 3rd,, but not for the 4th 5th and 6th,, i guess 4-5-6 clutches engage but car not moving,,

my first guess was a broken 4-5-6 intermediate shaft (stock),, but what confused me is that the bucking became worse enough to hear the tires locking and barking,,

checked oil,, no smell,, no discoloring,, no debris whatsoever,,

please,, help and advise,,
thanks,,

[realcanuk]

It sounds like you had an issue with the build right from the start, which would only get worse, better. The tuning school settings are for a stock transmission. With different clutches you would probably need different pressures, and possibly volumes.
I have not heard great things about those alto clutch packs. I rebuilt my trans with stock clutches, adding a few extra, and so far its working fine.
It is possible that you broke the intermediate shaft, (I twisted mine), and your original problem has become worse also. You wont know until you open her up.. What fun....

[kj217]

It sounds like you had an issue with the build right from the start, which would only get worse, better. The tuning school settings are for a stock transmission. With different clutches you would probably need different pressures, and possibly volumes.
I have not heard great things about those alto clutch packs. I rebuilt my trans with stock clutches, adding a few extra, and so far its working fine.
It is possible that you broke the intermediate shaft, (I twisted mine), and your original problem has become worse also. You wont know until you open her up.. What fun....

could it be the 4-5-6 piston?

[realcanuk]

could it be the 4-5-6 piston?

I am not an expert so I am not sure. I work on my own car but that's about it. I think your 4,5,6 clutches might be burned and welded together. That happened to me and the car moved in lower gears but locked, unlocked, made noises. It was not drivable at all really.
I really think guessing is futile and you need to open it up.

[kj217]

It sounds like you had an issue with the build right from the start, which would only get worse, better. The tuning school settings are for a stock transmission. With different clutches you would probably need different pressures, and possibly volumes.
I have not heard great things about those alto clutch packs. I rebuilt my trans with stock clutches, adding a few extra, and so far its working fine.
It is possible that you broke the intermediate shaft, (I twisted mine), and your original problem has become worse also. You wont know until you open her up.. What fun....

which 456 shaft replacement you got? where?

[realcanuk]

Since the shafts are made in canada, I got it directly from TCS, but it is sold elsewhere also. I believe PATC and century sell the TCS shaft.

http://www.tcsproducts.com/products/product/707/

[realcanuk]

This is what my stock one looked like after a few launches... not a great picture but you can see that it is twisted at the end of the splines.

[kj217]

i am sold to stock clutches with extra plates for the next build,, but how many extra clutch/steel plates for each pack?
what clearance?

[kj217]

here is a log,,
as you can see,, TCM applied max line pressure (290.x psi) to 3-5-R few times in 2nd gear,, this what made the car barking,,
another thing,, no 3-4 shift time logged,, if my issue was the shaft,, 4-5-6 would engage normally,,
any ideas?

[realcanuk]

There is no way to know what is wrong without tearing it apart. If the intermediate shaft broke, 4, 5, 6, would not engage. Actually, I am not sure anything would engage.

The best info I could find for building these things was here... read through it and then make some decisions. Good luck and post up what the problem was when you figure it out.

http://forum.grrrr8.net/forumdisplay.php?f=57