3.91 Diff Install.

[beta]

Originally Posted by Gtfour

The difference between 3.62 and 3.91 is almost the same as 3.91 and 4.10.

The difference from 3.91 to 4.10 is slightly more than HALF the difference from 3.62 to 3.91. 3.62 to 3.91 is 8%, 3.62 to 4.10 is 13%.

So really the choice between 3.91 and 4.10 is not an agonizing one, even if you chose "wrong" the difference is only half of what the initial jump was. And although the 3.91s are noticeable, it's not night and day; just a little more torque and a little more shifting.

Having said that, I'm happy I went with 3.91. Especially because I might do airbox or a supercharger mod in the future.

[inTgr8r]

Originally Posted by Z4Murder

The car feels absolutely awesome. This break-in period can't come soon enough. Zero leaks, no added noise, driveability hasn't changed much at all. I'm obviously cruising around at slightly higher RPMs now, but nothing too extreme. The few pulls that i have done so far, I can definetely feel the added torque. I have to say, for the z4m, gear swap-out is the best bang for your buck mod IMO.

$600 total covers the 1200 mile fluid change. Great service from the guys at Competition Transmission. Took a look around their huge shop, It's clean and they've got some mean all out drag cars.

Originally Posted by Gtfour

I had a 3.91 last summer and I have a 4.10 now, go 4.10!! And I have a ESS vt445!!!

The difference between 3.62 and 3.91 is almost the same as 3.91 and 4.10.

Originally Posted by seank

What a great combo: fun and reliable. You must have a huge smile every time you drive.

Originally Posted by Gtfour

Need to admit that the 4.10 is one of the best mod I did to the car! It's so fun when a car is rev happy.

Even with the SC, the 4.10 is very streetable. All the gears are shorter. First gear is still useable on the street. 2nd gear is border line on the track when you floor it. There is wheel spin up to red line but if you go a bit smoother on the gas pedal and try to get maximum grip, you can still use 2nd gear even on the track. Let just say the gas pedal isn't an on/off switch like before

Originally Posted by philjw

Just do the 4.10! I'm still in my break-in period, but this mod was absolutely worth it. Obviously haven't been to the track yet, but first gear is very useable. Granted, I don't have a supercharger like some other folks here... In any case, just do it!

Originally Posted by beta

The difference from 3.91 to 4.10 is slightly more than HALF the difference from 3.62 to 3.91. 3.62 to 3.91 is 8%, 3.62 to 4.10 is 13%.

So really the choice between 3.91 and 4.10 is not an agonizing one, even if you chose "wrong" the difference is only half of what the initial jump was. And although the 3.91s are noticeable, it's not night and day; just a little more torque and a little more shifting.

Having said that, I'm happy I went with 3.91. Especially because I might do airbox or a supercharger mod in the future.

BASTARDS!!!! ....the lot of you.






.

[Blind32]

Originally Posted by inTgr8r

BASTARDS!!!! ....the lot of you.






.

I'm with you. I've already put a beating on my bank lately.

Yet I still read this thread...

[007MCoupe]

This thread and CRFine's build thread ar what make me spend money.

[gmd2003]

Yep doing a 4.10 REM polished BMW Motorsport final drive with a 3 clutch 30/60/90 mechanical diff was the best mod I have done on my tracked Z4M . Really adds a ton of torque to the wheels , and the upgraded diff from diffsonline
makes a huge difference in putting the power down out of the corners .Not to mention its bulletproof for track work . Oh and it's fantastic with a blower ( I have 8000 track miles with on my VT-1 445 kit , and just upgraded to VT-520). I am running 265/285 sport cups and the power is very usable even on the street . Just do it !!!!

[Z4Murder]

Originally Posted by dubsesd

If you were doing it again, would you do 4.10?

I was going back and forth with this for a while, but i'm totally satisfied with the 3.91s. I can feel the added torque, and I haven't even beat on the car too hard yet while i'm waiting for the break in period.

Headers and other mods are planned for the future, especially since i now paid the car off. Being a power junkie, yea i would say i should've gotten 4.10s, but If i wanted a really fast car, I honestly wouldn't of bought the M coupe. I'm really happy with this car OVERALL, and the minor mods that i'm doing.

Originally Posted by mgwatson48

Where is the cheapest place to buy the gears alone?

I couldn't tell you, Turner was the only place I knew of before, and they're not listed on the site anymore. Maybe contact them and see if they have any.

Originally Posted by beta

The difference from 3.91 to 4.10 is slightly more than HALF the difference from 3.62 to 3.91. 3.62 to 3.91 is 8%, 3.62 to 4.10 is 13%.

So really the choice between 3.91 and 4.10 is not an agonizing one, even if you chose "wrong" the difference is only half of what the initial jump was. And although the 3.91s are noticeable, it's not night and day; just a little more torque and a little more shifting.

Having said that, I'm happy I went with 3.91. Especially because I might do airbox or a supercharger mod in the future.

I'm on the same page as you.

[beta]

I missed mgwatsons48's question, cheapest place for gears when we looked was Bobby Rahal bmw. Check out the thread here. We also sent out the gears to get shot peened and REM polished. All together me and finnegan got an excellent price.

[mgwatson48]

Originally Posted by beta

I missed mgwatsons48's question, cheapest place for gears when we looked was Bobby Rahal bmw. Check out the thread here. We also sent out the gears to get shot peened and REM polished. All together me and finnegan got an excellent price.

Thanks Beta!