The E46 M3 came with the M Variable limited slip that is known for a relatively short life span (right around 80k miles). We can refresh the M variable limited slip for a stock rebuild. We have found that using a 3 clutch limited slip with either the 35/60 or 30/90 ramp angles for a much longer life span and better all around performance. To get the most performance on the track, we would recommend changing the gear ratio to 4.10 for the 6 speed cars and 3.85 for SMG option.
Diffsonline builds a wide variety of BMW differentials in house to accommodate the several different differential housings used in modern BMW's. We start by cleaning the differential housing, then select the industry's finest ring and pinion gears, apply the desired clutch packs and options, and finally carefully assemble the housing to be shipped to your door.
The first decision to make when buying a custom differential is to determine the gearing you want. The gear ratio determines the number of revolutions of the wheel for every revolution of the drive shaft. The higher the gear ratio, the more RPM's an engine must turn to keep your speed constant. Take a look at our RPM / MPH chart in Technical Information to see how various ratio's may affect your cars performance.
Lastly, there are some upgrade options that may be selected including ring and pinion polishing for reduced friction / lower temperatures, upgraded rear covers, as well as miscellaneous bolts and fluids.