6-speed?

[blykins]

Guys, if you actually look at the difference between a T-45 and a T-56, the gears are actually pretty close to each other. The only difference is with the 6-speed, you get two overdrive gears, which really wouldn't help you any in racing anyway. What it would be good for is crusing on the highway with a really low rearend gear.

Here's the difference:

T-45 T-56

1 -- 3.37 3.36
2 -- 1.99 2.07
3 -- 1.33 1.35
4 -- 1.00 1.00
5 -- .67 .80
6 -- N/A .62

So it's not like swapping trannies is gonna give you a more narrow gear range or wider gear range. The only difference is the range in overdrives. So with the T-45 you could probably run a 4.11 and that would be equivilent to running a 4.30 with a 6-speed and a higher overdrive gear.

I got these ratios straight from Tremec's page.

If I were running a big low rearend gear, I'd want the extra cog for gas mileage purposes...but if you're anywhere in the 3.27-3.73 range, you should be fine without it.

In the Vettes and Vipers (Z28's and Trans Ams too), the 6th gear is usually even higher than that... a .50 ratio. I've driven all of these cars, and when you shift them into high gear at around 65-70, they run at around 1100-1200 rpm.

But I guess my main point that I'm stammering around is that the 5th and 6th gears are overdrives anyway, and wouldn't help you any...in a road race or any other situation except cruising.