Post Number: 233
|Posted on Friday, 04 March, 2016 - 12:35 am: |
I'm finalizing the rebuild of the gearbox on my '79 Shadow. It al went smoothly, having installed new clutch packs, some bushings and seals.
I followed an excellent manual on how to rebuild the GM Turbo 400 Transmission (by C. Ruggles) : after remounting the oil pump the book says to check the clutch packs with compressed air through the respective holes in the casing.
Each time you should hear a distinct "clunk". I can only hear the clutch pack "clunk" for the intermediate clutch. For the direct drum and forward clutch I can only hear the compressed air blowing back.
I dismantled the gearbox again but cannot find anything wrong.
Is this "compressed air" test reliable or should I just go ahead and reinstall the gearbox ?
Post Number: 1927
|Posted on Friday, 04 March, 2016 - 10:05 am: |
Have you tried moving the gearbox selector arm to each position before trying the compressed air?
My suspicion is the valve body settings need to be such that all positions have to be checked as individual clutches may be isolated depending on the gear selection.
I do not recall using the compressed air test when I rebuilt the T400 in DRH14434 but that was a long time ago and I may be wrong.
gordon le feuvre
Post Number: 105
|Posted on Friday, 04 March, 2016 - 08:18 pm: |
HAVE YOU READ THE MANUAL IN THE POST WAR TECHNICAL SECTION. I UNDERSTAND THE AIR PRESSURE NEEDS TO BE AT LEAST 70PSI. I DID GM 400 COURSE AT HYTHE RD IN EARLY 70'S AND SEEM TO REMEMBER THAT THE AIR TEST WAS TO CHECK THAT THERE WERE NO MASSIVE AIR LEAKS ON CLUTCH PACKS FROM PISTON ACTUATION SEALS. MY FEELINGS ARE THAT THIS WOULD BE DONE AS ACTUAL GEAR TRAIN WAS BEING REBUILT, BEFORE VALVE BLOCK RE-ATTACHED.SORRY, CAN'T BE MORE SPECIFIC.
richard george yeaman
Post Number: 467
|Posted on Friday, 04 March, 2016 - 08:56 pm: |
Benoit considering the replies from the previous two posts and the fact that you have checked your work my answer to your question would be to fit the gearbox and I am sure that having taken on this job in the first place that you have faith in your own ability cheers.
Post Number: 234
|Posted on Friday, 04 March, 2016 - 10:49 pm: |
Thanks everyone, I will leave it as it is and continue installing the gearbox.
When blowing compressed air in the holes the air is blowing back, not escaping somewhere else, so I guess Gordon is right in that the air pressure needs to be quite high to get the clutch packs to move.