Trans Replacement info

[Richard D.]

Was wondering if anyone can tell me if you have to pull the motor to replace an auto trans in a 68.

I'm going to embark on changing the current auto back to the original M-21 4-Speed.

The 68 shop manual doesn't say it's necessary, but someone told me you had to.

Thanks,

Rich

[William C.]

Re: Trans Replacement info

I believe tyhe problem is that if you have a 4-speed frame, the crossmenber that the trans mounts attach to is welded in place, where the auto trans cars use a removable crossmember to allow the auto trans to drop out. If you have the 4-speed frame, likely the engine/trans will have to be removed as a unit

[Stephen L.]

Re: Trans Replacement info

If you have the engine hoisting equipment I find it easier to pull the engine/trans as an assy. Then when you have it out on the floor its much easier to retrofit everything together. This is even more true if you are going to need to work laying under the car.
You may also want to look at clearances for the transmission tailshaft if you are going to attempt to leave the engine in place.... You'll need to slide the trans rearward to clear the engine, flexplate etc. and you may run out of room.
The frame cross member is NOT removable as it is on passenger cars.

[Joe L.]

Re: Trans Replacement info

Richard and Bill-----

Yes, that's correct. If your car was an original 4 speed, it will have the welded transmission crossmember. With that crossmember, I don't think that you can remove the THM transmission without pulling the engine/transmission as an assembly.

[Richard D.]

Re: Trans Replacement info

Thanks Guys.

It is a welded crossmember, so it's not looking good from here!

I did not know that the auto equipped 68's had bolted in crossmembers.

Did not notice that in the AIM manual.

Again, thanks for the advise, I think I'll look at pulling the engine and trans out when I get to it to effect the swap.

Rich

[William C.]

Re: Trans Replacement info

I don't believe it will show up in the AIM as the feature is not used for the Factory Build process. The only way it would be noticed is a note about a different frame part number for the auto trans cars. I think that was also the only service frame, but I could be wrong on that.

[Joe L.]

Re: Trans Replacement info

Bill-----

Original-type manual transmission frames with welded-in transmission crossmember were available in SERVICE for 69-78 Corvettes until late 1981. At that time, the parts were "consolidated" and a removeable auto transmission crossmember type frame became the SERVICE frame for all 69-78 applications.

For those that are interested, for 1963-1967, ALL Corvette frames used welded-in transmission crossmembers. For 1968 to 1978, manual transmission used welded in crossmember and automatic transmission used bolted-in crossmember. For 1979-1982, ALL frames used bolted-in crossmember.