I'm going to be installing either 3.73 or 4.10 gears. I think either would be fine but I'm trying to best match the ratio with the cam I'm running (in sig) to the speeds I'll typically be running. The cam power range is listed at 1800-5800. The 3.73 gears would give 72mph at 1750 RPMs. The 4.10 gears would give 72mph at about 1925 RPMs. Which ratio would generally give better highway mileage? The lower one or the one running in the power band?

 

The 3.73s should give you better mileage, but I doubt that you'll be able to notice it. You might as well hop on the wagon with everyone else and get 4.10s. I've got a set of Motive 4.11s waiting to go in, can't wait, I'm still stuck with my auto 3.23s. Plus, an aftermarket cam may make it a little harder for your engine to pull on the bottom, so all the more reason for 4.10s.

 

if you are gonna stay NA there is no question... get the 4.10 because you wont notice too much of a difference going from 3.42 to 3.73 .

 

Well I emailed Comp Cams and asked them what they thought. They replied that I would actually get better mileage with the 4.10 gears because they would be cruising in the power band. Interesting. By the way, are Motives and GM gears the same thing? I've read that GM gears are quietest but I haven't been able to find any part numbers.

 

check www.thunderracing.com I belive they sells GM motive gears.

good luck! you will love the 4.10 you feel like you have a differnt car!

 

Does Motive make more than one quality of gears? I just found some for a great price, new Motives, and wonder if they are the same as I would buy anywhere.

 

AS FAR AS I KNOW THEY ARE ALL THE SAME.

 

There's not a lot of difference between 3.73's and 4.10's in an A4, so there can't be much at all in an M6!!

 

my vote is for 4.11, you will love it

 

Yeah there's a guy named diff-man on ebay I think, got mine for $145 shipped, new in the box. They're actually 4.11s, 37 & 9 teeth, I don't know if other manufactureres use 41 & 10 for 4.10 or what. I think Strange supposedly has the strongest gears, but they're quite a bit more expensive as well. I bought the complete install kit and a mac girdle as well to try to keep them from breaking.

New Era Performance parts has some of the best deals on drivetrain parts right now, free shipping on some stuff.

With all these people saying 4.10s make your car feel different, it has me wishing for a warm weekend. 3.23s + T56 suck.