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  1. #1

    Default TH 350 in a 1957

    I recently retired and am now ready to get my 57 Vet out of mothballs. However, Iím also ready for no clutch driving. Iíve seen references to other automatic transmission swaps, but I have an extra TH 350, so thatís what I prefer. Is there a conversion kit available that is essentially a bolt up job?

  2. #2
    Administrator Tom Bryant's Avatar
    Join Date
    Nov 2000
    Edgerton, Ohio, United States
    1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
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    Default Welcome to the CAC

    Good question. I would think that the problem, if there is one, would be in trans tunnel clearance. I now that there are guys on here that have done various trans swaps and there are a few companies that offer complete 5 speed kits for these cars. There are also companies that offer complete change-over kits for auto overdrives such as the 700R4 but they may not be Corvette specific. There are several companies that advertise in the back of Hot Rod and Car Craft, among others, every month. They should be able to answer your fitment questions.

    If I was doing this I'd check into an automatic overdrive conversion. With gas prices being what they are the lower rpm at cruise speed could save you the cost of the conversion over time. Plus you get a lower 1st gear for better acceleration from a stop.

    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

  3. #3
    Join Date
    Jun 2007
    Madison, AL
    1956, 1956, 1979
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    I just went through this with my 56. The biggest problem will depend on whether or not you have a 57 engine in the car. The 57 engine block has no provisions for bolting up a starter (it is on the bell housing). The TH 350 has no way to mount a starter.

    I ended up using the starter adapter mounting plate sold by Classic Chevy International (and others I am sure). It is a 1/4 thick steel plate that fits between the engine and transmission.

    You will also need a transmission mount adapter plate. Something similar to the adapter plate that was used on 1962 Corvettes, but remember, your transmission is pushed back 1/4 inch so you will need to slot the holes 1/4 inch.

    Also, you will need to find a way to mount a shifter. The TH350 does not have mounting holes for a floor mounted shifter. You will need to make some sort of bracket to mount the shifter.

    I made a combined transmission mount adapter plate and a shifter mounting plate. It worked out well.

    Also, the TH350 will need an external cooler, so you will need to run cooling lines to the radiator area. I used an aftermarket trans cooler.

    And last, you will need to get a vacuum source for the modulator valve. I put a fitting in the base of the single four barrel carb.

    Not a exceptionally difficult job, but quite a few details to think about.

    FYI: Your TH350 must be the short tail housing version, and you must also change the driveshaft yoke.

  4. #4
    New Member
    Join Date
    Oct 2009
    northern California
    54, 60, 63
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    Quote Originally Posted by emccomas View Post

    I made a combined transmission mount adapter plate and a shifter mounting plate.
    Ed, can you post a picture of this adapter/mount? It sounds like the key to a successful installation.


  5. #5

    Default TH 350 in a 57

    It's been awhile since I posted my question, but now I'm back.

    I have a radiator that is for an automatic transmission and an engine with the starter mounted to it. Also, a spare TH 350 with a short tail housing. If someone can make me a "combined transmission mount adapter plate and a shifter mounting plate", I was would most elated beyond belief.


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