I decided to fix the small leak on my differential today as it was leaving some drops under the car. At closer inspection it appeared to be leaking from the cover, a closer inspection revealed a few cover bolts not as snug as should be.

So, got 2 liters of 80/90W gear oil, removed the cover, cleaned and applied RTV, re-installed and re-filled. Looked ok for a few minutes until... leaks again!

It is actually leaking right through the steel cover. Looks like the cover has rusted to the point that it has small pinholes and the oil is leaking through, now much more than before with the new oil. These holes must be awfully small since the inside of the cover showed nothing.

So.. Here's my question:

Can I JB-Weld or epoxy the outside of the cover? Anyone have experience with either? Will it resist the oil? If so, should I apply epoxy or JBWeld to inside as well? Obviously I will prep the surface properly for adhesion, just wondering if it will hold up to the oil. What is better? JB-Weld or some type of epoxy?

Also, anyone know what the sensor is for on the diff cover? Fluid level?


Your responses are much appreciated,

Andre Corriveau
Ottawa, Ontario
87 745Ti AW71, 420,000 kms

You were lucky to notice the leak before you lost the oil. I was not so lucky and ruined the differential and all the bearings. An axle from a wreck fixed it but the whole job was big, dirty and expensive. $100 for a new cover is a considerable bargain and is highly recommended.

Hi Guys,
Thanks very much for the info.
After removing it a second time, it appears I will need a new cover. The existing one has so much rust that JB Weld will not adhere properly and has too many holes to make it worthwhile. The amount of welding necessary will probably kill the sensor and price to do so will be at least half the cost of a new cover.

Anyone know quick sources for a new cover in Canada other than dealer?
They are indicating a one week delivery, price $99.50 Cdn.

Thanks again,

Andre C.
Ottawa, Ontario
87 745 Ti

I would say go to the junkyard and pull one. I might coest you about 5-10 bucks at most.

If you can remove the sensor, you might consider welding or brazing the
holes. That would (in my opinion) be a more permanent repair than
adhesives or sealants.
--
George Downs, Bartlesville, Oklahoma, Central US

I am a big fan of JB Weld, but it might be a bit thick for this job. I think I might just go to the junkyard and pull one. If not that, a less viscuos slow drying epoxy would be my second choice. Check with 3M and Devcon.

The sensor is the pick-up for the speedometer and odometer.

Dan

JB Weld is pretty good stuff. I would clean the cover THOROUGHLY (any residual oil will cause the adhesive to fail), using lots of rubbing alcohol and even running it through the dishwasher. I would remove any rust on both sides, and recoat with POR-15 paint or appropriate rust-resisting paint or galvanized spray coating. Then apply JBWeld to the outside surface, making sure it penetrates the holes. Then paint again and reinstall.