Will somebody let me know if the Tremec T56 magnum transmission will fit in my 1966 Cutlass F-85?
I am replacing the original power train from bumper to bumper. I am replacing the original 330ci engine with a 350. In place of the original M-21 I would like to have the 6-speed Tremec.
I am thinking 9" Currie rearend with 3.73 gears.

 

Everything that I have looked at online states that the 6-speed will not fit in that chassis without tunnel modification. Some of the "kits" even come with sheet metal material for that purpose. There are versions of the 5-speed available which will fit without tunnel modification including the newer TKX model. That would be my choice.

 

Jim is correct about the fit of the T56.

In the days before conversion kits, I put a T56 in my 1970 Cutlass (1970 probably had a bit bigger tunnel than yours). I had to remove the tunnel back through the floor pan brace to give enough room. The T56 is a TALL transmission.

Construction and completed shots below...

Gary

The hardest part, psychologically was cutting up that rust-free floor.


My stick position ended up 3" farther back than that on the factory 4-speeds.