A few questions since I've done my t56 swap.
1. What gear ratio do you have?
2. What rpm in sixth gear at 70 mph
3. What rpm and mph do you cross the line in the quarter mile at?

I'm thinking of going with a 4.11 or 4.30 when I swap my nine inch in. Currently I have 3.73 and it's pretty lame.

 

Btw this is a street/strip weekend car. So I don't care about drivability. Heavily built 383 on a 250 shot of nitrous

 

I don't get it. If you don't care about driveability, why do you care what the rpm is at 70mph.

All of this is VERY easily calculated.

http://www.wallaceracing.com/gear-speed.php

 

I was just saying I don't care bc it's not my daily driver, but I do hit the highway sometimes cruising around. Currently sixth gear seems useless unless I wanna cruise 120 mph

 

Thanks for the link

 

I've used a T56 with 3.70's and 4.11's and I don't get into 6th until around 80MPH........

 

I don't get it guys. Not sure whats up with your setups, but I am running a 0.5 ratio 6th gear T-56 with 3.27 rear gears and have no problem at all running 6 at as low as 65mph. With that said, I am in the process of changing to 3.73's.

 

I had 4.10s in my car with a T56 and I hated them. First gear is useless so I swapped them out for 3.73s and I am a lot happier.

 

That's why I don't like auto's,........ Always trying to keep me @ 1500RPM ! 6th gear under 2000RPM and the tourqe simply doesn't exist; Like driving a T5 @ 30MPH in 5th........


A lot of guys prefer 3.73's; I Like the 3.70's- just like the 4.11's better. I'm used to driving a 95 LT1 T56 with skip shift so I'm pretty used to reving first gear higher than "normal".

 

Yup I get it. But nothing beats it on the highway with the cruise control on. It really quiets down the engine and better mileage. I still find the torque more than enough to maintain 65 on any hill.

 

mine has a 4.10 rear gear with 28 inch tall tires. it runs at about 80 to 85 in 6th gear. anything less and 6th gear is useless. it is like 1900-2100 rpm at the 80-85 in 6th gear.

on the strip im getting really hurt. i go threw the trap at just a bit over 5000 rpm. i run a 12.8-13.00 at 106-109.

i either need a shorter tire or a taller gear. if i had it over again i would have done a 4.56.

i think im just going to turn on some nitrous and keep cruising in 5th gear on the highway lol

 

I used a 3.73 for a while when I was troubleshooting some noise in my 9". I literally felt like I lost 50rwhp going from the 4.11 to the 3.73.

4.11 or steeper all the way!

 

thank you. two answers to the actual question. im definitely going with at least 4.10. my only fears are too many rpm at around 130 mph trap times. 7000rpm will be fine, but any more ill be shifting to fifth lol

 

I had a forth gen LS T56 car with all the bolt ons, 17x11s and a 4.10. I LOVED IT!!! at 75-80 it was sitting at around 2200. on street tires I couldve leave the line at more than 2k without slipping the clutch something terrible. I wouldnt change a thing, I absolutely loved 4.10s on the street. Once the car was rolling it would hook well though.

 

I have 3.70s and its around 1800 RPMs at 70+ mph.

The problem with 4.10s is that the gear teeth are so small for the stock 10-bolt that theyre very weak, especially considering its a manual trans and it will see severe shock loads. You could make 4.56's work easy as far as the gear ratios themselves go, but just remember 5th and 6th gear are not meant to be driven under load/acceleration. They werent built to be strong enough for that, so there is a point where going higher doesnt get you anywhere, but its a long way from 3.73s and 4.10s.

If I had a 9 inch I'd go 4.56's probably.

 

Same for me. I tried a 3.27 rear and it felt much slower. 3.70 is the lowest I'd want and whenever I upgrade to a 9"/s60 I'll probably opt for 4.10.

 

Keep your cam in mind to. Mine doesn't work real well below 2k with the low 6th gear. So if you go with a big cam 1700 rpm wont work to well.

 

I have a t56 with the .5 ratio and 3.23 gears. I can shift to 6th at like 60. I also routinely shift to a gear to cruise at under 2000 rpm if possible. Love the low end torque of a 350.