I have an E46 M3. You have an E46 M3. We both want the same thing: gears, headers and sex. Let me tell you, the bang for the buck is with a set of gears – 3.91 or 4.10 final drive gears, to be exact. The problem for most of us is that upgrading the E46 M3 gears from the factory 3.64 to a Motorsport 3.91 or 4.10 is expensive however we may have found a way to cut those costs by hundreds, if not thousands of dollars.
A new BMW Motorsport final drive gear can set you back close to $1000. Then you factor in supporting replacement hardware — the carrier bearings, races, etc to rebuild your diff. Add another $250-300. Need a new differential while you’re at it? Oh, this is adding up quick. But what if you could obtain the 3.91 or 4.10 gears for a fraction of the cost if you sourced them from another model?
Here’s the Deal
BMW used two different sized differential housings. Lower powered vehicles came with the 188mm sized differential while the performance models used the beefier and stronger 210mm size. The E46 non-M3 uses the 188mm differential while the E46 M3, E39 M5 and various other models use a 210mm gear set. This is why non-M owners who want a limited slip differential can’t simply swap in an M differential.
So the E46 M3 should accept a final drive gear set from all other BMW 210mm differentials BUT not all gears are built the same. Some have special coatings designed for Motorsports use. You’ll want to contact a BMW specialist such as Diffs Online for more detail.
Below are a list of models that came with or had a trim that included a 210mm final drive gear set. Be sure to do your own research before making any purchase.
Models with 210mm Gear Set and Final Drive Ratio
- E34 M5 Euro before 6/94: 3.91:1 Final Drive
- E39 M5: 3.15:1 Final Drive
- E60 M5: 3.62:1 Final Drive
- E53 X5 4.6is: 3.91:1 Final Drive
- E53 X5 4.8is: 3.91:1 Final Drive
- E90 M3: 3.85:1 Final Drive
There may be more models with 210mm gear sets but looking at this the clear winners are the X5 4.6is and 4.8is. If you are lucky enough to find a used differential on Ebay or your local salvage yard it may be a save you a half dozen Benjamins or more. If you are comfortable working on your own car and have experience rebuilding differentials then you might be able to upgrade your E46 M3 gears for less than $600.
If anyone has done this upgrade, can confirm or deny the above, please leave us a note in the comments below!