Hello all! I am new to the forum. I am currently in the process of restoring a inherited 81 corvette with the super t 10 transmission. I have an LS 2 motor and am looking into transmission options. With 55k miles on the stock trans, my question for you all is as follows. What is the drivability like with the 6.0 ls2 mated to the OG Super T 10, 4 speed????? I like the idea of the classic 4 speed but understand the performance of the T56. Money is always a thought, but my plans for the car are not racing related. I plan to cruse down the road at 70 "ish" mph and roast the tires when I want to. Nothing crazy. Please, any knowledge on the matter or pictures you can provide are much appreciated. Thank you!

 

First note a T56 Magnum shifting is night and day vs any of the 4 speed options. Test drive a C6 corvette to get an idea vs super T trans.

My 78 Changed from a L48 350 to a ZZ383 with T56 Magum 6-speed 2.66 1st , 0.63 6th and 3.08 Rear Diff. Roast Tires not really but over all great performance for road racing to street cruzing , plus 27.4 MPH @ ~ 70mph 1700 RPM.

Then changed the ZZ383 to a LS3 / 480 and Roast Tires became possible but also a great 33.1 MPG. The LS3 made the car much more a overall performance car and great combo for the T56 6 speed. The next change will be the Diff to
a 3:36 to better match the C6 corvette (LS3 T56 speed & 3.42 Diff) Great overall performance setup.
1978 LS3 Swap Completed. - CorvetteForum - Chevrolet Corvette Forum Discussion

AS for a a 1:1 final drive trans ratio would put you @ 2700 RPM with a 3.08 Rear Diff so much higher RPM @ 70mph.

For my T56 swap
T56 Magnum Install 78 Corvette. - CorvetteForum - Chevrolet Corvette Forum Discussion

 

Agree with the above. I went from a Gen 1 SB with a Muncie to a TREMEC 5 speed then to a T56 6 speed with an LS3. No comparison. The double overdrive and shifting smoothness is night and day. I now own an 07 Z06 and the shifting and performance of the modern transmission far outweighs the “classic” old school 4 speed.

 

There are some things you want want to look into before you really get started on anything. If my research is correct your year of T10 has a first gear ratio of either 2.88:1 or 3.44:1. Your rear end ratio is likely a 2.72. A healthy LS motor is gonna twist up a T10 transmission, the Dana rearend, or both. All of these components were designed with the 70s fuel crunch in recent memory with sub 200 hp small blocks with sub 300 ft/lbs of torque. If you run it hard your gonna find the weak link. A stock LS1 back in 97 made 345 hp with 350 ft/lbs of torque.

Let’s talk about a T56 for a sec. The T56 platform at best has a 2.97:1 first gear ratio, and most are 2.66:1.

The way I’m seeing it is you want to change not only the tranny but the rearend too. Depending on the T56 in question you want no less than a 3.42 ratio (you can get away with a 3.23 if the T56 has the 2.97 first gear). Which means you want to find an older rearend (preferably out of a big block car) and retrofit that into your 81. Personally I would be looking for either a 3.70 or a 4.11 (preferred) rear out of a big block car if you end up with a T56 with a 2.66 first gear.

Those are my thoughts though. The older cars already have heavier rears so not so much a problem for them.

 

Every time I drive my car I want another gear. I even find myself checking to make sure I'm really in fourth. And I only have 3.55s. Dump the four speed and get an O.D.

 

plus the modern engine would require some kind of adapter or special bell housing to put an old-school trans onto it.

 

I think I read somewhere that the Super T-10 is rated at 375lbs of torque, so dependent on your build (and your right foot habits) it could be a bit small for your application. I switched from my Super T-10 to a TKO600 and think it was the best upgrade I have done to the car (and mine has been frame-off). Having that overdrive makes it a totally different beast. Having said that, plenty of folks are using the T5 5-speed which is only rated at 300 lbs of torque without issue. It really is driver/use dependent.

W/respect to your rear end durability, a lot of that is going to be dependent on your tire selection. A well built stock unit (see posts by GTR1999 for more info) is good to a little over 400hp give or take how you treat it. If you use standard tires like BFGoodrich T/A's, the tires will lose traction first and reduce the stress on your rear and universals. If you go with high quality/traction tires, you will be stressing the drivetrain a LOT more during hard launches as the tires will not let go and slip as easily.