E46 M3 rear differential seal

Today we have Damian’s BMW M3 in for a differential leak from the input shaft seal..

This is a common problem, however it’s fortunately quite low cost to have replaced.

This guide is a brief DIY, assuming you have some skills at car repair then this job is quite easy to do.

First place your car on a lift.

Drain the diff oil. New oil should be used at the end of this job.

Then you need to dismantle the exhaust system and lower it, either remove from the car or let it dangle if you prefer.

Then you must remove the exhaust heat shields, this is straight forward so I have not taken any photos.

Next up undo the rear propshaft bolts. Mark where the shaft lined up against the flange as it’s nice to keep things how they were.

Now seperate the propshaft from the flange, using a screwdriver.

You’ll then see this. The centre nut needs to be undone. Common practice is to mark the nut position so when you refit, it tightens to the same place. This is advised so as to not overload the diff bearing which can lead to noise or failure.

Wipe off the grease and undo the nut.

Then tap the flange out which will reveal the input shaft seal.

Remove the seal and this is the bearing talked about earlier.

New seal and lock ring, this should be replaced with new.

Fitting is the same but in reverse. Remember to tighten the nut accordingly and the prop shaft bolts. Don’t forget to refill your diff with new oil -Castrol Syntrax 75W140.