[PresaMat]

I was thinking. With all this talk of the super high revving new m3... Why dont we start looking at changing our rear gears? We have so much torque down low (especially in the ProCEDE'd cars) that I dont think we need as much gearing in the rear. If we to were to change from the 3.08 (in the manual) to something in the 2*s we would still have plenty of torque to take off but have the advatage of more time in first/secound/third etc. Im no expert on these matters so if anyone who knows more about this subject then I do would be willing to chime in with some advice it would be greatly appreciated!

Mat

[musc]

You aren't going to benefit as much from lower gearing with a turbo car that doesn't turn a lot of RPMs. As far as taller gearing, I would think the current gearing is a pretty good compromise. Going too tall will simply hurt acceleration, even with extra torque from something like the PROcede. You may be able to use a 2.73 gear or so, but I doubt the benefit would be worth the cost. The 3.08 gear in the MT is probably a good fit for this set up. If want to experiment, try running a taller tire.

[visor]

Initially, I thought you meant reverse gear...
But then I read it again, you meant rear diff gear...

Changing the gear/rear-diff to get stronger torque multiplier to the ground is very frequently done by modders. It is quite cost efficient.

Only potential pitfall is that the top speed in each gear is lowered, so if 0-60mph and 1/4 mile measurements are important to you (as it is to the general public and most if not all car mags), then that potentially extra shift to the next higher gear will waste precious tenths of a sec. Same goes for slalom testing and auto-crossing.

[PresaMat]

I was actually thinking of reducing the torque... since we have so much already. I would think it would give us a little more in the higher end.

Mat

[visor]

Originally Posted by PresaMat

I was actually thinking of *reducing* the torque... since we have so much already. I would think it would give us a little more in the higher end.

Mat

Oh, I get what you're trying to do...reducing the mutiplier instead.

Hmmm, I'm not sure what that would achieve. The corollary effect would be to potentially require a higher rpm in order to quickly launch from a standing start. And maybe you'll get better highway fuel consumption?

[carlson335]

So if the car is already speed limited to 155, what is a lower gear going to do other than slow acceleration. Before I saw the light, I used to have a Mustang Cobra (a 99). It was a real dog from the factory because Ford fudged the numbers on the engine output. Anyway, I changed the rear end on this car from 3.27 stock to 4.30. It was MUCH quicker in every gear, BUT I had to install a little black box to correct the odometer and speedometer. Apparently Ford's speed / mileage sensor was looking at engine speed rather than wheel speed. So the point is, BMW may have the same problem; be prepared to figure out a way to correct this error and get out your wire cutters unless someone has figured a crack on BMW's computer codes.

One last thing, my mileage went down after this mod because the engine ran faster by about 1000 RPMs - or just drive in a higher gear than you're used to.

[Couch]

Originally Posted by carlson335

So if the car is already speed limited to 155, what is a lower gear going to do other than slow acceleration. Before I saw the light, I used to have a Mustang Cobra (a 99). It was a real dog from the factory because Ford fudged the numbers on the engine output. Anyway, I changed the rear end on this car from 3.27 stock to 4.30. It was MUCH quicker in every gear, BUT I had to install a little black box to correct the odometer and speedometer. Apparently Ford's speed / mileage sensor was looking at engine speed rather than wheel speed. So the point is, BMW may have the same problem; be prepared to figure out a way to correct this error and get out your wire cutters unless someone has figured a crack on BMW's computer codes.

One last thing, my mileage went down after this mod because the engine ran faster by about 1000 RPMs - or just drive in a higher gear than you're used to.

Exactly, if you raise the gearing, as you went to a 4.30 in your 'stang your gonna have a lot quicker off the line acceleration. But lose top end speed. Lower the gearing and you should, in theory, increase the top end. I know 3.73 gearing is very popular in the trucks. I'd be curious what it would do in the 335. With the combined torque and hp, it would probably be a great gear.

[DrGP]

Basically, you can get a big performance upgrade with the Procede without doing any mechanical changes. $1300 and some install time and Voila, you have a beast. Although LSD would be nice.