5-speed and limited slip differential installed

July 31, 2008

I have owned my 1973 BMW 2002 for 3 years now and put in countless hours of work and changed out nearly everything, except the drive line. Two weekends ago I went up to my friends shop to finally change it all out. I have been running the stock setup from the clutch back for too long. Also, the lack of a 5th overdrive gear is hurting my gas mileage.

The install went pretty smoothly and took only a day to accomplish. While we were putting in the new transmission and driveshaft we also threw out the stock open differential for a 3.9:1 limited slip. I have said this after numerous projects before, but wow it feels like a new car! The transmission is smooth and the shift throw is much shorter and tighter. In conjunction with the new differential gear ratio the gets off the line quicker. Also, since power is put down the wheels evenly it comes out of corners like a race car. Previously with my open differential the car ‘wiggled’ as it regained traction after a hard corner due to the fact that is sends power down unevenly.

To see pictures of the installation check out the Flickr set.

Open differential versus limited slip differential

Open differential vs a limited slip

I’m not going to go into great detail regarding all of the differences because that can easily be Googled. I just wanted to show the the main difference. On left we have my stock differential which is an ‘open differential’. On the right we have my new Limited Slip Differential (LSD) with a gear ratio of 3.9:1.

The major difference and also the major weak point of the open differential are the spider gears. This allows the wheels to spin independently. With the car in the air, I can spin one back wheel and the other one will spin in the opposite direction. The limited slip on the other hand doesnt have those gears. Not only can it handle more power it also makes locks the wheels together. Putting the car in the air and spinning one wheel will make the other spin in the same direction. More information can be found at howstuffworks.com.

Categories: Cars

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