sschevellecutlass_Bob

Looking for help in deciding which transmission to match up to LS375 (480Hp) engine for 70 Cutlass. Always wanted manual tranny, but am thinking about the Cutlass as my daily driver. Have Chevelle which has TH400/Gear Vendor ( I was waiting for the Muncie 5 speed which never came out). Durability, Cost, ease of installation, fun factor, performance both off the line and highway, and blend of town/long distance capability are all factors. I know you can't have all of them, but would like to hear your thoughts/experiences. I know I want overdrive. 5 Speed is enough. Most likely 15 inch rims with no larger than 29" tires. Currently have 3.08 rear and would like to keep that or go up to no more than 3.31.

Thanks for your help.

61Bat

I had a Tremec TKO in my blown alcohol BBC 69 GTO and I really liked it. I had 411 gears and I could cruise at 75 mph no problem and it stood up to some pretty good abuse. I went with it over the T56 primarily because I didn't think I needed 2 overdrive gears and the T56 weighs 100 pounds more.

brownbomber77

TKO all the way....but you gotta cut the tunnel.

61Bat

yes. Totally worth it unless you have an uber rare W30 ragtop or a super original car imo.

sschevellecutlass_Bob

Thank you!

VC455

It may not be that much difference. Depending on how they are fitted, the difference is between 25 and 35 pounds.

olds 307 and 403

With such tall gears, get the TKO with the .82 overdrive gear. Don't waste any money on the fragile 4L65E, go 4L80E if you desire an OD auto.

young olds

I put a t56 in my 66 and pretty much never use 6th. Drops the rpm so low I actually burn more gas then 5th.

sschevellecutlass_Bob

Excellent info to know... Wow. thanks....

oldzzy

TKO 600 for me as well. Had to cut the floor, but no big deal.

VC455

The hardest part about my manual installation was psychological--cutting that pristine floor.

brownbomber77

A steeper rear gear can solve that "problem"....haha

young olds

It already has 4:10 in the rear, if I’m not doing 85+ 6th is just to low an rpm to be efficient(for my car)

young olds

Did you actually have to cut that much out? I barely had to cut anything in my 66

VC455

A T-56 6-speed is a large transmission. You must have accepted a greater engine-transmission angle. I tried to get the angle the same as stock, which required a lot of surgery. I didn't want any chance of having drive line vibration due to large u-joint angles.

young olds

No extreme angles in mine, I did remove the reverse lock out solenoid which actually gave me a ton of clearanc. Iirc I measured at the carb pad and was no more then a degree or so off. No driveline vibrations, i would be surprised if I did some hammering in there too.