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Old 04-07-2009, 05:08 PM   #1 (permalink)
Shawn D.
Harebrained Idea Skeptic
 
Join Date: Jun 2008
Location: Alpharetta, GA
Posts: 211

The White Car - '84 Mercedes-Benz 300td
90 day: 28.84 mpg (US)

The Blue Car - '86 BMW 535i
Last 3: 23.86 mpg (US)
Thanks: 19
Thanked 13 Times in 9 Posts
Differential Change from A 3.46 to A 2.93 -- Intended & Unintended Consequences

Y'all,

Since I'm about to take a 1400-mile trip to see interesting friends and places*, I recently changed out the 3.46 limited-slip differential (LSD) in my 535i for the 2.93 LSD out of my son's 528e (he went to a 3.25 LSD).

An intended consequence was getting better mileage for the trip -- I'm already getting ~2 MPG more in mixed commuting, and the car is much quieter on the highway, which led to an unintended consequence.

An unintended consequence was hitting 90 MPH when it sounded as if I was doing about 70 MPH! I'm also hitting the wrong gear around town, since 1st-5th now seem like 2nd-6th!

For the time being, the 2.93 will stay in, but I'll probably change it back to the 3.46 for the autocross season. Yeah, I know autocrossing ain't "eco," but it sure is fun!

-Shawn

*OK, OK -- I also installed the 2.93 since I'm installing a turbo in a couple of months.

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