: Transmission help!!



customGTP
02-04-04, 01:40 PM
hey guys I am debating matting two different transmissions up to my Northstar when I get it. Here are the two gear ratios..

--The manual 6 speed has a 2.66 first gear, 1.78 second gear, 1.3 third gear, 1.0 fourth gear, 0.74 fifth gear, and a 0.50 sixth gear ratio...final drive 3.42:1

--The manual 5 speed has 3.37 first gear, 1.99 second gear, 1.33 third gear, 1.00 fourth gear, and a 0.67 fifth gear....final drive 3.27:1

Help me out on which one would benefit the motor the most and efficiently
Thanx guys

Dubya
02-04-04, 02:27 PM
the 6 speed would be nice for the highway with that .5 6th gear, but the 5 speed has a much more aggresive 1st gear.....but is it needed?? how much is the car going to weigh? are the torque rating the same for the two?

jonrodman
02-04-04, 10:46 PM
I am not an expert, but if I were to try it, and use similar size tires, I would choose a transmission with the first and second gears similar to the ones that come in the STS automatic from the factory. My opinion is that I love the gear ratios in the STS. I think they are perfect. I love the fact that it pulls really hard in first and does not have to shift until around 50 mph at 6800 rpms. If the gear ratios were any higher, the tires would just smoke. They would not have a chance to get a grip, and the 1-2 shift would be earlier than it has to be. Second gear should almost take the car to the end of the quarter mile without shifting again. Third gear is good for over 150 mph. If you put a nice overdrive ratio after that, you have achieved nirvana.

customGTP
02-05-04, 12:43 AM
I do want a very responsive gear selection.. I'm building this car fo roadracing. I will have to relearn my engine RPM's and everything I know but I'm liking the T56 as well as the 3650 tremec as listed above

zonie77
02-05-04, 01:02 AM
For road racing I'd go with the 6 spd. Not as much RPM change. You aren't worried about starting from a dead stop as often. With the rear axle gears you listed It would be the 6 spd for me! With the double OD you might even go to 3.73's. What tire size?

Tirerack.com lists O.D. of most of their tires and revolutions per mile. It might help you decide.

customGTP
02-05-04, 04:16 AM
i will be running a 275/40/17, a stock WS6 wheel, should do the trick...
Hmmmmm unsure

customGTP
02-06-04, 11:43 PM
I like the agressive gearing but like the OD gearing for all the distance traveling I'll be doing..

zonie77
02-07-04, 03:32 AM
With the 6 spd and 3.42's final drive =1.71,with 3.73's =1.87.

With the 5spd and 3.27's final drive = 2.19 (assuming my math is correct).

The 6 spd gives you lower rpm in 6th.

1st gear 5spd with 3.27=10.909
1st gear 6spd with 3.73=9.90

A little less gearing off the line but much closer shifts with the 6spd.

I've driven Vette's with the 6spd and it is really nice!