In Reply to: 3.64 or 3.91 Differential posted by SamK on December 21, 1999 at 14:33:09:
: I appreciate the comments of some already, but I have one remaining question on deciding whether to change the differential. I currently have a 3.64 and am putting in the Korman stage one engine. I can either have some work done on the 3.64 or change the axel to a 320i and put in a 3.91. I'm not sure i understand the precise difference between better low end speed on the 3.91 and better top end performance on the 3.64. Is the difference really noticeable for a daily driver. TIA. 74(Inka)
I would use the 3.64 if ANY highwaay driving is anticipated. The 3.91 is good for hillclimbing and drag racing when combined with only a 4 speed.