My2kz28

iTrader: (1)

Got a buddy with a 93 lt1 z 28 m6. He has a procharger with twin intercoolers, boltons (lontubes, borla) rocker arms and MSD 6a. There are 3.23's in the 10 bolt right now, but he is buying a 12 bolt soon. I have heard mixed opinions on the topic. I have heard it is best to go 3.42 because it allows you more time to stay in boost. I have also heard to go with a numerically higher gear ratio to get to peak boost quicker. Which is recommended and why?

cablebandit

iTrader: (37)

3.23-3.50 for turbo
i went 3.73 from 3.23 and switched back to 3.23. For a s/c car i'd say 3.42-3.50

My2kz28

iTrader: (1)

I called ATI and one guy recommended a 3.73 gear ratio. A local performance shop here in town recommended a 3.42- 3.73. Since I have been getting mixed opinions, im thinking the 3.55 gear ratio might be the best ratio.

RW99

I'm very interested in this topic, too. The single turbo build on my car is shooting for 550 rwhp and I'll need to put a 12 bolt in to handle it... for my M6, should I order the new rear with 3.42, 3.73, or 4.10? Arguments for one or another?

Thanks for any info,

Rich

cablebandit

iTrader: (37)

i had a 3.73 ...with the converter locked in 3rd gear, I was hitting 140mph at the end of the track 9trapping 136mph) with 26" tires at 7300 rpms. Even with 28" tires I think thats like 7000 rpms...too much for me. Ran 10.16...2 weeks later with 3.23 ran 10.12 and much safer rpm

My2kz28

iTrader: (1)

Thats cool....i dont think i will be running 10's for a while...focusing on mid 11's. Anyone know what gear ratio is best for centrifugal supercharged cars?

Jake19_2

I've heard 3:42's are good for supercharged cars as well.

JohnnieMo

I have the stock 3.42's in my car. No way it is sufficient. I would like a 3.90, but I think 4.10's are a better bet for other reasons. I know others with my setup are loving the 4.10's. But it also depends on your MPH. I am at a high elevation, so my MPH isn't as high as it might normally be. And you don't want to make that 5th gear shift. Run the numbers in a gear ratio / MPH converter.

http://www.xse.com/leres/ss/calculator.html

Stick your redline and your tire size in there and play with the ratio until you get the right MPH in 4th gear. But give yourself some room to grow With the 3.42's, my car is good to 138MPH.... but since I'm running 115MPH, I'm losing a lot of 4th gear. So a 3.90 would be ideal for me.