1978 manual is now a automatic whats wrong?
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Heel & Toe
Joined: Oct 2012
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1978 manual is now a automatic whats wrong?
I recently bought a 1978 and they removed the t10 4 speed and replaced with automatic not sure which one yet but when driving im noticing a knocking feeling or thump under my seat or something.i was told that if there is a swap done that you need a drive shaft cut for it .is that true?I want to go back to manual 4 speed but will have to locate all the items.Tranny shifter linkage from pedal to clutch etc. etc. etc..i guess the knocking could be from improper installation considering they put the engine accessories on backwards so there no telling. any input?
Le Mans Master
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From: Galloway Twp. NJ
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depending on what auto they put in the driveshaft might not need to be cut... I'd be more worried about how they got the auto trans in there with the welded transmission crossmember...
Thread Starter
Heel & Toe
Joined: Oct 2012
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transmission
transmission does shift properly except i have a difficult time getting it into park from drive.may be linkage or something and i cant get it into first manually because leather boot bunched up in the way and the fabricated some makeshift console improperly..when in drive it shifts fine but that thumping worries me
Race Director
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From: Shamong, NJ
The thumping you hear/feel, may have nothing to do with the trans swap.
Check the bushing mount at the front of the rear end. The one where the rear where the front bracket, bolts to the frame. Is this bushing is shot, you will get a thumping as the rear end moves around, and since it's in the center of the car, not far from the "seat of your pants", will may seem like a trans problem.
Gwank's right, manual trans 78's, had a welded crossmember. Only OEM automatic cars, had the bolt in one.
Check the bushing mount at the front of the rear end. The one where the rear where the front bracket, bolts to the frame. Is this bushing is shot, you will get a thumping as the rear end moves around, and since it's in the center of the car, not far from the "seat of your pants", will may seem like a trans problem.
Gwank's right, manual trans 78's, had a welded crossmember. Only OEM automatic cars, had the bolt in one.
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Original 78 manuals were welded. You can convert to bolted and it's somewhat likely the person who installed the automatic did.
The only way I can imagine putting an auto in a fixed transmission car would be if the engine and trans were installed together.
Look under the car near the door. Inspect the transmission crossmember with your eyes. On each side, a stock bolted crossmember will have 2 bolts going into the frame from underneath, through the crossmember, and one through bolt going into a hanger.
If you're not sure, you can take a few pics and we'll likely be able to tell you what you have.
Melting Slicks
Joined: Jun 2006
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From: S Nevada
I suggest you put it up on jackstands and take a good look, or if you are not comfortable doing that, take it to a competent shop (preferably a shop that has knowledge of these cars) that has a lift for a thorough inspection. If the latter, ask the mechanic if he can go over the inspection with you. You'll be able to get a better idea of what was done. Many corvettes are modifyed by cutting the solid crossmember and building bolt in ones to make transmission service easy. Especially for those who race their cars and need to do more frequent servicing. I agree with gbvette62, there are a multitude of things that could cause a thumping sound other than the transmission. Some are easy fixes, some more costly.
Last edited by Sunstroked; Oct 11, 2012 at 11:54 AM.
Race Director
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From: San Jose CA
Go look under the frame.
Also, if the center console is out you'll have a decent idea whether it was an auto or stick. In 78, an auto floorpan is different and has a recess for the shifter to rest in. A manual would have had a straighter floorpan with a cutout for the shifter.
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....all 1980-'82 Corvettes had the removable crossmember whether it was auto or 4spd. Yeah, I know all '82s were autos....when I changed my old '75 Corvette from a Turbo 400 automatic to a correct Super T10 4spd, the trans yoke and driveshaft did not need changing.
...does it have the welded(might be bolted?)tab on the frame below the mastercylinder where the one end of the Z-bar bolted there?
Last edited by Paul Borowski; Oct 11, 2012 at 09:59 PM.