I thought about adding 4:10's just go get my car to run 11.5's but I like my gears so much I dont think I can change.

 

65mph is @ 1750rpm with 4.10's and a stock size tire, and @ 1600rpm with 3.73's and a stock size tire.

And you were only doing 86mph @ 2100 rpm with 3.73's, not 100.

 

new update with my gears... (3.73 in an auto) overdrive on the highway definatly woke up. It accelerates easier than before without having to downshift. Driving 70mph, I'm spinning about 2500rpms, so your M6 will be lower than that. I still cant get on it yet because i gotta take it easy for like the first 300,400 miles or so. Im definatly happy with them. If your worried about breaking your rear end, just go with the 3.73's. People have 4.10s break more often.

 

I have decided to get 4.10s. Now can anyone post a link to some good ones? What about the slp gears?

Also found these http://www.mofbody.com/forums/viewtopic.php?t=26611

 

Slp gears are overpriced. (like most of their stuff) I think Motive makes their gears anyways, so why not just motives. They can be had for about $160 shipped.

Since your doing 4.10s it may make sense to get richmond gears as people say they are a little bit stronger than others. The only downside with the richmonds is they create more noise than others. Those are going to be more expensive at a little over 200 i think.
I got mine here, seems the price went up, but shoot him an email and see what he can do for you.

 

richmonds are the ones that always break. i run GM 4.10s

 

245/50/16 = 245mm tire height = 9.64 inches
9.64 inch tire + 16 inch rim = 25.64 total wheel height (diameter or 2r)
perimiter = 2*pi*r
perimiter = 25.64 * pi
perimiter = 80.55 inches

So each time your axle turns you go 80.55 inches. (axle not driveshaft)

Now for the differential, with 4.10 gears and let's say our T56 Transmission is in the 6th gear which has a ratio of .5 you would get the following.

(rmp of engine / transmission ratio) / read end ratio * perimiter of wheel = inches per minute

(6000 / .5) / 4.10 * 80.55 = 235756.098 inches per minute
= 14145365.88 inches per hour (235756.098 * 60)
= 223.25 miles per hour (14145365.888 /63360) as there are 63360 inches in a mile

Now if you need to adjust just plug in the number that you have (tire size, rear end, gear, etc...) and you can decide on which gears to use by yourself without all of us telling you 'how it feels'.

As a personal opinion, I have 4.10 and a cam and I love them!

 

You have to count the tire profile twice when calculating the diameter of the tire.

 

Oops...updated the post with the corrected number....now you can really see it...even with 4.10s you still have way too much top speed for most places.

 

Or, if you're lazy like me, you can go to

www.f-body.org/gears

and It'll do everything for you, and even present it to you in a nice chart.

 

Not to mention, I dont think an F-Body has the areodynamics to ever hit that kind of MPH inless it was built some type of all-out race car. The amount of power, weight reduction, and suspension work to hit that kind of speed unimaginable.

If your concerned about top speed, dont be. I would bet that even with 4.10s they make peak power at 5th not 6th

 

I need a 3 series right?

 

Its 100. I drive the car everyday. BTW, Its an M6 not an auto.

I actually just pointed it out to a friend today as we where driving down the highway. Unless my speedometer isnt on par with my tach wich Im pretty sure they are as when I ran my car at edgewater I usually trap right on the money and the rev limiter Kicks in at 6700 Everytime.

 

Actually, You have me second guessing it. Im going to have to do some extensive research becasue my dash has been acting up and numbers dont lie. But it is what my tach shows.

 

It's wrong. Its physically impossible for you to be going 100mph at 2100rpm with 3.73's and a stock size (245/50/16 or 275/40/17) tire. Either your speedo is off, or your tach is off. Did you ever get the speedo recalibrated for the gears?