Yes, when Little G went from 3.23s to 4.10s in his '02 V6/M5 he lost a few MPG on the highway, but picked up a few around town.

- Justin

Ok, so I finally found an Eaton Posi, now I'm looking for the gears. What's the difference between thick and thin, and which do you recommend.

Thick is for a 2 series carrier, thin is for a 3 series.

Yeah youll go with the thins if your using 3.23 or numerically higher gears. I, tho havent gotten them yet, I would go with 3.42. If your drag racing go 3.73 or 4.10, but if your autocrossing, or just looking for a better takeoff, but nothing insane, go with 3.42.

I can't see how 4.10s WOULDN'T help autocross.

:stupid:

Nothing like quicker acceleration out of a corner.....

- Justin

well like for someone like me, driving all the way up to N. Jersey would kill gas, and yeah itd be nice for autocross, but idk about a daily driver ratio, adn dont 4.10's whine a little?

Whining is not associated with a particular ratio. It has to do with how well the gears are set up, and what the tooth angle is. Some gear installers just put everything in and that's that- regardless of how things like pinion depth and backlash get set. They half ass it and you get noisy gears. They will also make up ******** dismissive excuses if you press them about the noise. Good gear installers will install and tear down as many times as it takes until the measurements fall within the proper range.

How do you measure for backlash?

Ah, ok, thats why i never put 3.42's or 3.73's ( at first I wanted 3.73's, then decided 3.42 would be more within my range) cause I thought after a certain ratio they would whine, good info, ill keep that in mind.

Rather than type it, here is a good explanation:

http://www.rps4wd.com/tech/RandP/backlash.htm

One way a set of 4.10's might become a factor is if you run out of rpm which could require a gear change to third gear. The gear change if it occurs at a bad point on the track could unsettle the car, maybe....Or by not shifting you would be on the limiter which is holding you back and potentially putting the valvetrain under undue stress.

Generally, no the 4.10's wouldn't hurt, but every course is different and there could arise a situation where the additional gear could cause a problem on a long blast if you don't have additional rpm range to go with it....

Chris