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Re: 540i Chip and differential ratio change (archive)

[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]

Posted by Bill mitchell on September 20, 1999 at 13:00:54:

In Reply to: 540i Chip and differential ratio change posted by Ron M on September 19, 1999 at 17:58:24:

: I have a 1994 540 auto and am considering two performance mods - a JC chip and a lower differential gear ratio. I live at high elevation in Denver and am curious if the JC chip really does much up here. Also on the lower diff ratio I have the following questions:

: 1) Is the speedometer affected? If so, can some compensation be made?
: 2) Are gears available or do you have to go with a whole new differential?
: 3) Would the auto trans be affected?
: 4) Is it worth it? Because of the power loss here I'm looking for acceleration improvement but would be open to other ideas (a $7500 supercharger is not an option right now).

: Any experience/knowledge would be greatly appreciated. Thanks.

I recommend the Jim C. chipand a 3.15 diff. I put a 3.15 in my six speed 540 and the difference is dramatic. Its the best bang for the buck you can get. A used diff out of a 530 is sometimes available(that's where mine came from) and mine was limited slip to boot. cost about $600 and I made the swap myself. Dinan and Korman will charge you nearly $2000 for one of theirs.

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