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Old 12-30-2012, 06:22 PM
Microtesties Microtesties is offline
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Location: Concord, NH
Join Date: Oct 2012
Posts: 101
Mein Auto: 1990 BMW 525i
Question Differential swap

Greetings everyone! I've been working a lot with my new (to me) 1990 525i and want to throw some upgrades at it. What I've been focusing on recently is swapping out the differential. I think I want to lower the ratio, which I know sounds counterproductive, but my reasoning is that the current final drive is 3.75, and first gear is 3.84. Together making first gear just about useless for anything faster than 10-15mph. SO if I were to drop the ratio to around 3 I would get a lot more out of first gear. Does anyone know what differentials will bolt right up in place of mine, or even with some minor modifications? The ratio of the 1987 E30 325 and E28 528e is 2.93, could this fit my e34? I would love to hear everyone's opinion on this swap, since when talking diff swap, you usually go up instead of down. Lastly, will changing the ratio mess up the speedometer reading? Thanks in advance!
Year: 1990
Model: 525i
Transmission: 5 speed
Mileage: 250k
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