Re: Leaky Differential (archive)

They fill from the back of the differential cover, same type plug as the drain. It's above the rear support member. Changing the seal is involved, you have to remove the exhaust to get the heat shield off which covers the driveshaft which must be removed . . . etc. When removing the input shaft, scribe or punch a mark indicating the position of the collar nut so that it can be tightened to the same pre-load when assembling. If you find it was loose when you get into it, Bentley calls for a torque of 137 ft-lb. The spec for new fluid is Hypoid 90 gear oil. If it's a limited slip, then it may also need the friction conditioner additive, although most synthetic gear oils will not require it. You'll need to buy a cheapie plastic pump to get the oil into the fill hole, & fill it until it runs out of the hole. To do a complete job, you might want to consider replacing the seals for the axle shafts as well. Now you're talking involved. Bentley covers it in section 331.

gale
92 735i
148k

Was under the car today, a 'class 1' (wet with oil and drops forming) leak on the diff at the seal where driveshaft hooks in; oil all around so its spinning off while driving too. What kind of oil should I put in it, where is the fill plug and how do you check the oil level? My truck was easy enough, take out the plug, stick your finger in the hole, if the oil is level you are good, if not add gear oil. The only plug that looked obvious was on the bottom side of the diff. If I take it out all the oil would follow I think!. Also, can a 'crunchy' sound which I thought was my wheel be the diff or the driveshaft (ouch, big ticket items now).

Thanks for your help.

Stu
94/740i/71k/US

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