rear-end gears

[chuckz]

does anyone know what the stock rear end gear ratio is in a 96 318is?
M44 motor with 5 speed. dealer has no clue, my engine revs at 4000 rpm
at 140 kph (not mph). i'd like to swap gears for more top end
thanks

[Furious]

3.91 rear diff is what you have.... if i were you id look at a 3.46 (320 rear diff) you will gain more top end, but wont loose to much acceleration, there are other possibilities to look at as well the 3.38 which is out of the automatic M3's (hard to find and expensive but has limited slip) the 3.23LSD from the manual M3's, the 3.15 LSD and non-LSD from the 325's.. the trade off of course is the closer the ratio (higher the number) the quick the acceleration becomes but you lose top end. and if longer the gears (lower the number) the top end increases but you loose accel power.

[tomctx]

Some cars also seemed to have a 3.64 final drive. Check with www.diffsonline.com for possibilities.

[chuckz]

thanks, judging by diffsonline i have the 3.91 gearing.
next question is where to search for 3.46 gear besides the dealer?