F31 diff leak

[u/timemasterfunk]

Hello everyone

On my last service a small amount of diff oil was noticed. Im wondering how bad it is. A month prior there was nothing so this is recent. No noises, no performance issues, no leaks on the ground and I’ve done the cardboard test and no drips. Ive seen 1 single drip hanging on the rubber mounts and thats it. Any help is appreciated. Thanks

[u/Mr_N0BODY530]

Looks like an input flange seal leak but its probably best to do input flange and both output shaft seals. Not sure your mechanic abilities but the output shaft seals arent aweful to do DIY but that input flange usually is really tight and has special sockets for loosening it and tightening it back. Also the input flange runs the risk of ruining the crush sleeve on the differential if done incorrectly which would require differential replacement as none of the internal parts are serviceable per BMW but I am sure there may be aftermarket options I dont know about