Question 3.73 Diff [Archive]

ZeroG

08-31-2004, 09:09 PM

Is ther anyone out there with a 5spd that did a 3.73 Diff conversion? I would like to know what kind of a gain was seen, and how much top-end was lost? Also did you think it was worht it?

-Chad

KIRASIR

09-01-2004, 04:15 PM

Tis are limited to 110mph, so top end stayed the same. The RPMs are about 500 higher, and the car definitely has more pick up.

If you have an open diff then I would recommened the upgrade, if you have a 3.45LSD then there is no point.

SL

Is ther anyone out there with a 5spd that did a 3.73 Diff conversion? I would like to know what kind of a gain was seen, and how much top-end was lost? Also did you think it was worht it?

-Chad

bmwracefan

09-10-2004, 01:54 AM

You can acheive the same gearing by switching tires to 205/45-16's. Lowers the car too.

L84THSKY

11-10-2004, 04:12 PM

Are you saying that 205/45/16's are smaller in diameter than stock? That would increase the RPMs. What "lowers" the car, bigger wheels or smaller, almost seems like a mind game, when I think about it?

You can acheive the same gearing by switching tires to 205/45-16's. Lowers the car too.

GDB

11-10-2004, 04:50 PM

Why would it not be worth it to put a 3.73 into a LSD? It seems to me that the smaller gear would be more useful with the added traction that a LSD offers. But with an open diff, then it would just increase tire spin at lower speeds.

Silver00spike

12-13-2004, 01:58 AM

Tis are limited to 110mph, so top end stayed the same. The RPMs are about 500 higher, and the car definitely has more pick up.

If you have an open diff then I would recommened the upgrade, if you have a 3.45LSD then there is no point.

SL

110mph? Are you sure? Ive gona faster then that in my 97 DASC car, with stock ecu. I think it hit a wall of air or limiter at 125 IIRC

AlaskaBlue

12-13-2004, 03:44 AM

Ok, I have hit 120 with a Dinan Chip, Exhaust, K&N, and 9 lb flywheel, and it wasn't that the car was straining. I have the 3.45 LSD by the way.

GDB

12-13-2004, 04:23 AM

These numbers are with a redline of 6500, 205/55/15

Gear Top Speed
3.45 129
3.73 119

These are based purely on gear ratios, there are other factors that come into effect, namely wind resistnace. The numbers also change with tire size. If you want to play around with the numbers then go here (http://www.car-videos.com/tools/speedrpm.asp)

AlaskaBlue

12-13-2004, 04:54 AM

My Ti came will 205/60/15

GDB

12-13-2004, 06:09 AM

My Ti came will 205/60/15

oops, you're right. I have 205/65/15s and I keep forgetting what they came with stock. So those speeds should be slightly higher, but probably not more that 1 MAYBE 2 mph.

AlaskaBlue

12-14-2004, 04:38 AM

Can I buy just the rear end gears I want from the dealership? If not where else would I be able to find them?