November 2008. Odometer 276000km. One of the big differences between the e30 325i and 325e/325 models is the rear differential. A differential transfers power from the driveshaft to the wheels, while allowing the wheels to spin at different rates around corners. Most 325i cars ship with a 3.73 "limited slip" differential ("LSD"), where the 325e/325 cars ship with an "open" differential, with a ratio that favours fuel economy over power and handling. In my case, I had a 2.93 open differential. At the recommendation of Dwight at Zionsville Autosport, I decided to upgrade my differential to a 3.23 LSD (purchased through Zionsville).
Project Total: $1150.00
A *very* noticeable power increase and much improved handling. The entry to every gear is much peppier. In average street driving, the handling is impossible to notice, but you can feel it under extreme conditions in two ways: 1) it's much easier to do "doughnuts" (i.e., spin in a circle) 2) it's much easier to recover from oversteer (i.e., to perform "drifting"). Both handling improvments make a big difference at, say, an autocross, or when reaching the limits of your tires on the track. If you're doing any kind of motorsports and have a stock e30 325 or 325e, you pretty much have to do this upgrade at some point.
Here's the 3.23 differential before installation:
Here's the 3.23 differential installed:
