Went about helping my grandson change the differential gasket and fluid on his 1990 240 DL. First and foremost, the fluid was as dark as used motor oil, and the gasket was so old and crumbly it looked like it may have been the original. The magnetic drain plug had about an inch of metallic "paste" on it as well. When I got the cover off, the gears and carrier looked fine, no abnormal gear patter wear of chipped/broken teeth.

The interesting thing is that the differential cover had an electrical plug connected to what I assume is a sensor (?) in the cover. No mention of what this could be in my Haynes manual or Chilton Manual. Soooo Anybody know what it is and its purpose??

Thank you

 

That would be the pickup for the ABS tone ring in the differential.
The paste on the plug is metal particulate, the plug should be magnetic. Wear is normal and if you didn't notice anything abnormal, then it's not bad for a 1990.

 

It's the speedometer pickup for 1986+ cars and doubles for ABS on the 89+? cars

 

Thanks