corvette trans issue
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 45
Likes: 0
corvette trans issue
hello all. i have a 79 vette with an auto and the trans is giving me issues. when i take off the engine sounds like its moving 30 but im moving 5. it does that in 1st and 2nd but when it shifts to 3rd it sems fine. i replaced the trans filter again(replaced it 500 miles ago) and it was dirty. thought that would do it but no. anything else it can be before i go to the rebuild? rear diff issue? thanks
Racer
Joined: Mar 2002
Posts: 406
Likes: 1
From: Maroochydore QLD
Nothing to do with the diff, probably nothing to do with a rebuild and everything to do with band adjustment, just take it to a trans specialist and have it serviced, should be like new for not too many dollars.
Cheers, Dennis.
Cheers, Dennis.
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
your transmission has two planetary gear sets. bands are used to hold different parts of the gear sets in a fixed position; the bands are "pinched" by servos in the hydraulic system, and depending on which part of the gearset is held by the band(s) and which rotates, the input shaft--connected to the engive via the torque convertor--will spin the output shaft at different speeds (or a different direction in the case of reverse gear). Aussie is saying the bands that control your 1st and 2nd gear aren't functioning correctly, and FWIW I agree
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 45
Likes: 0
What kind of work does that intail? If I have to drop the trans I might as well rebuild. It seems like the torque converter. It works fine in reverse. It speeds up in 3rd but still with very little power. Off the line it revs up but doesnt move very fast. When I come to a stop it sounds like something is binding. Or even grinding but more like if I had locked up brakes. do you still think thats what it is?
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Racer
Joined: Jan 2008
Posts: 288
Likes: 0
From: Schaumburg Illinois
What are the chances you knocked the vacuum line off the vacuum modulator? They are not held on with a clamp, just pressed on so they can come off pretty easily. On the passenger side of the trans, should be silver ot copper color with a small nipple on it, the nipple should have a rubber hose on it, should be hanging near by.
Intermediate
Joined: Dec 2008
Posts: 47
Likes: 0
From: cary nc
if its a turbo hydromatic 350 trans, it would only have one band and i dont think it has an adjustment. sounds like the clutches are worn and not holding or the pressure isnt strong enough to make them hold. the modulator valve is only for part throttle shifts and the trans would still pull properly even if the vacuum line fell off. not too sure about the torque converter but if it pulls when it gets in drive its probably not that either. a trans shop is probably your best bet. when you get it rebuilt, put in a shift kit so the shifts will be more rapid and the clutches wont have time to drag and create friction which is what causes them to wear, plus you will be able to churp the tires between shifts.