gear ratio

[Gcruz]

Hey Reg if you do read this, what gear ratios are offered for the BDR and what are the cost. My engine has roughly 585hpand 600lbs of torque. Im using the stock 15 wheels and have a 2:95 first gear ratio.

[Boudy]

Gcruz: We don't stock replacement diffs. Rebuilt units start at $2,000 so it's best to pick one up from a BMW salvage house. Most of them will give you a lifetime replacement warranty. You'll pay from $300 to $600 this way. Below are some ratios and the cars they come from to help you in your hunt.

Model (E36) Stock Gear Ratio
318iS, Ti Manual Transmission 3.45
318iS, Ti, Automatic Trans 4.44
325 Manual Transmission 3.15
328 Manual Transmission 2.93
325/328 Automatic Transmission 3.91

I personally think that our stock 3.10s would work really well with 585 HP. Low for a smaller motor, but your torque should drive right through them.

Boudy

[tfarhood]

Boudy,
It is interesting that this question came up. I was told that the BDR's have the 3.10 gears in them. I have build #101 and I wanted to double check that number before purchasing my speedometer gears. I checked it the old fashioned way by lifting the rear and spinning the differential for one tire revolution. I got 3.50 three times (I had to tripple check). Maybe it is really 3.45. Anyway, I'm happy it is a little better for me. Just glad I checked before getting the wrong speedo gears.

[Boudy]

The stock ratio is 3.10 but they get some 3.45s and 3.91s occationally. Check with Reg to verify what was installed in your car.

Boudy

[CSCHWER]

I'm not familiar with the BMW models.
Will a 318i-m 92-98 3:45 differential fit?

Chet

[uncltodd]

Gcruz-

I talked with Boudy and Reg both yesterday about #139. (MINE! MINE!)

With a 351W @ 385-400 HP, I decided that the 3.47 screws were a good compromise between acceleration and top end. Keep in mind, the nearest track to me is Texas Motor Speedway, about 150 miles.

I would never street race, of course.

I figure for this kinda money, another $600 is cheap to keep from kicking myself in the butt for the rest of my worthless life.

UT