Ask an HDC Tech: the Transmission Conversion Q&A

[Ron@HDC]

Originally Posted by pokey64

620HP at flywheel.
Main goal is for a comfortable/enjoyable car for our family to cruise in. (Our boys will be 1 and 4 this summer) Mostly cruising in town and countryside, occasional spirited driving, maybe 1 Good Guys autocross per year.
Undecided on clutch style. We have a mechanical in our Camaro with a BBC and TKO600 and it’s fine.
275/40/18 rear tire.
Highway speeds around here are 55-60 freeway are 70-75. 1800ish RPM?

Okay. We have two T-56 Magnum transmissions that will work in your Chevelle.

One is a 2.66 first and a 0.63 6th. This transmission will turn over ~2075RPM @70MPH in 6th gear, and ~2070RPM @55MPH in 5th (Which is 0.8).

The other is a 2.97 first with an 0.5 6th. This transmission will turn over ~1,650RPM @70MPH in 6th, and ~1900RPM @55MPH in 5th (which is 0.74).


Because of the low RPM in 6th gear for the 0.5, I would suggest you look at the 0.63.

The T-56 was designed around LS motors and since you will be installing it behind a big block, you will essentially have to start from scratch regarding parts. HDC does have a parts kit which includes everything you need to put this transmission in to your Chevelle, except the driveshaft. Rather than listing all of the parts here, I'll give you a link to the page on our website. Click here to see the HDC T-56 Elite kit for your Chevelle.

Unfortunately, I do not have any pictures of our tunnel patches installed in a '66 Chevelle with a T-56.

If you have any other questions or would like to go over your driveline conversion more in-depth, don't hesitate to call us at 707-535-3030.