Differential question

[gwittman]

I replaced the differential input shaft seal using the BMW method 'without replacing the crush sleeve'. I resolved the minor leak but am a little concerned about my work. I ended up rotating the nut about 5-10 degrees farther than the original position and still did not quite get to the specified torque. I decided to go ahead and assemble everything to see how it works.
There are no unusual noises and the force to rotate is about the same as it was before. What I do find is after driving around town (stop and go) for about 10 miles at under 50 mph and moderate acceleration, the differential is near hot. When I put my hand on it I can keep it there but it is near the point I would have to pull it away. I am guessing the temperature is around 150 to 160 F. That seems a little warm to me. Does anyone think that is normal? I have ordered a crush sleeve but would prefer not going through all that trouble needlessly.

 

[eriknetherlands]

I've never measured my diff, but I'd say that compares to how my diff operates (operated, it's dormant for 6 years now). From the design (cooling ribs at bottom) you can tell that they are designed to get warm.
Some (sportier) diff's have more fins, or even separate oil coolers. Quick googling gives ranges from 120 F to 240 F between town driving and pulling heavy loads uphill (other car model).
160F doesn't seem bad to me in that light, but again; I'm just googling here.

Should you go and replace the crush sleeve, take care that likely you'll need a new oil seal as well.

 

[gwittman]

I had already planned to replace the seal again if I decide to replace the crush sleeve. It is inexpensive but it takes a lot of disassembly to get to it and the crush sleeve.
I thought the same thing about the cooling fins. If it has them it must get pretty warm. I will continue to monitor it and slowly work up the speeds and time at speed to see if it gets really hot.