do I have a 2.93 or 4.10 diff ratio?

[UpOn3]

Just got my car. Assume stock 4.10 diff, but seems to be sluggish. When driving on the freeway in 5th doing exactly 75 MPH, the engine is turning just about 3400 RPM. Does this sound about right to for 4.10? thanks guys.

If you guys know where to find a graph of diff ratios, please let me know. Thanks.

[dashboardmonkey]

Sounds like you have a 4.10. There is a tag on one of the diff cover bolts with the ratio stamped in it.

I will type what i remember for ratios that can fit an e30
2.79
2.93
3.25
3.46
3.64
3.73
3.91
4.10
4.26
4.46

[bmwm42]

4.10 is what you have

[dashboardmonkey]

Its the same numbers i run at that speed. I haz 4.10

[bmwm42]

Your right andy

[irish44j]

for future reference, this is a useful tool

http://www.differentials.com/technical-help/differential-gear-ratio-calculator

[UpOn3]

Thanks all. Confirmed on tag today, I do have a 4.10. It said "4.10 9772", anyone know what 9772 means? I'm quite surprised given that I read many w/ 4.10 feel the need for taller gearing. 4.10 feels geared high for this motor. I think I'd be happier w/ a 4.27. Anyone know which BMW models were equipped w/ a small or med case 4.27 LSD?

BTW I used a calculator before I posted and my numbers came up somewhere btwn a 3.93 and 4.10. I guess it's likely both the tach and speedometer are off...

[Tisoc]

318 verts were equipped with 4.27 diffs, but good luck finding an LSD with that ratio, they're quite rare. My old cabby actually had one.

[dashboardmonkey]

E36 318ti auto also had a 4.27 diff.