I am about to do the swap and I am trying to decide between 3.73's and 4.10's.

 

Either one will work. I have 3.42's and need a little bit more gear.

 

3.89

 

i will be going with 4.10s when i put in my six speed. there is plenty of overdrive in the six speed to keep highway driving at sane rpms. the more gear the better for acceleration

 

That's not the only issue.

In the quarter, you don't want to shift into an OD gear before crossing the traps. Ideally, you'll cross them just under redline in your 1:1 gear (that would be 4th for T5 and T56 guys).

If your trap speed is sufficiently high and your red line sufficiently low, you will run out of MPH in 4th gear before finishing the race. 4.10s would have been too much gear for me based on what I'm eventually going to run, so I went with 3.89.

As an example:

Consider a hypothetical car with a 5500 rpm redline, 4.11s, and 245/50-16 tires. At redline in 4th, the maximum speed is ~102 mph. If you trap higher than that, you'll have to shift into 5th. With 3.89 gears, it's almost 108mph. Change to 27" tires, and it's close to 114mph. Raise the redline to 6000, and it's 124mph...

 

Umm as long as you don't get 2.77s. Believe me on that one 2.77s and t56 suck. 1st gear feels good but 2nd is a dog. If you have a stock tpi I'd get 3.42s, and if you have a modded tpi intake I'd get 3.73s. If your not running tpi, I'd get 3.73s-4.10s if you have a high redline.

 

I have been running a 2.77 nine bolt since I put the T56 in last summer. Believe me, you do not want to have 2.77s, they really do suck. I am just trying to get some money together to get to Miles for some gears and a carrier, hopefully I will get it done early this summer.

Tim