This article covers the installation of an Aftermarket Tremec T-56
Six-Speed Transmission into my 1975 (Type C-3) Corvette. I bought
the transmission from Forte's
Parts. It differs from the transmission GM uses in its F-body
sport cars. This transmission is made to use the original clutch,
bell housing and speedometer plug/cable, out of older sports cars,
including most C-3 Corvettes. This conversion is NOT a bolt-in operation.
You will need to alter or fabricate several items on the car, in
order to install this transmission.
My vehicle is a slightly altered 1975. Originally this car was
an L-48 with a 4-speed. After a wreck in 1994, I replaced the small
block with a big block and the 5-speed transmission with an automatic.
To accept the automatic, I had to modify my existing cross-member.
My cross-member was originally welded, so I cut mine inside the
frame, welded on end plates and now mount each side with four bolts.
The specific way I modified mine is not mandatory for this installation,
so you can modify yours anyway you please, as long as it will accept
this transmission and can be removed from the vehicle. Also, I eliminated
the cable (on manual transmission cars), which eliminated you from
removing your ignition key without first putting the car in reverse.
This cable was attached to the shift arm of the old transmission,
but the new transmission has an internal shifting rail, so there
is no place for attachment. I can now remove my key, no matter what
gear, including neutral.
IMPORTANT NOTE: The installation
of this transmission was done bolted to the motor and installed
as a unit. I did not put it in by itself, with the engine already
installed. Therefore, I cannot say that you will be able to install
it separately, although it does appear highly possible to do so.
You would need to, at the least, remove the shifter from the transmission
and drop the back of the engine down enough to allow insertion of
the input shaft into the adapter plate and bell housing. You may
need to remove the fan blade and/or distributor and loosen the motor
Major Items Needed For This Swap
· After market Tremec T-56 Six Speed Transmission
· Custom-built transmission cross-member. (Approx. $200.00)
· Turbo 350 transmission output shaft yoke for Corvette (Approx.
· Driveshaft shortened and balanced (Approx. $50)
· Console cover plate modification
· New shifter arm or modify your old one.