New guy... Diff ratio question

[909SCUM]

Hello....

I am building a 92 325i for the 1/8th mile drags out here in So. Calif.,....
The car is stock with an automatic and the A/M button next to the shifter... of course it runs better in the 'M" mode manually shifting the car down the track...

My question is... The stock diff has a tag on it that reads 3.91 ratio, and the car is slug off the line and does'nt come alive until about 3500 rpm.... I've read alot on these threads that the 3.91 is suposta be a killer diff to have... but I'm wondering if there is a 4.11 type diff avalible for my car?... Or if the problem is something else?

Sorry for the long post.... any help would be great.

[Neel]

www.diffsonline.com there is a diff calculator on that site that might help you out.

[Paradigm_Guy]

A 4.45 is available. But the problem is that you have an auto 325, not your gearing.

[Manny G.]

problem #1 = auto transmission.. very slushy transmission and will never give you the true feeling of a 3.91 diff. a 3.91 is a super high ratio differential for a 325, but if you're just doing drag strips, then its great ( personally liked the 3.73 myself for everyday) .. keep in mind that the higher u go above 3.91, your car will just rev faster 0-60 and not have much of a top end at all.