I have 2006 F150 with 3.73 LSD rear diff. and it has a small problem. It is leaking around the rear cover. It isn't a severe leak just an occasional drip, but the bottom of my rear diff. is always covered with fluid. And I was curious if anybody else has had this problem.
But, I guess the the leak isnt the main part of the problem. I only have 14,000miles on the truck and it has been leaking since I bought the truck new over a year ago. BUT, i have taken my truck into the dealership twice to have the seal replaced under warranty and both times I was told the the leak was normal, and it was nothing to worry about. But, on my last oil change I checked the fluid level of the rear diff. and the was hardly any fluid left in the diff. I was a mechanic for Toyota for 2 years so I could easily replace the seal on the cover on my own, but the would cost ME time and money. So Im starting to think that I should just let the rear diff run dry and hopefully burn up or explode, and then have Ford replace my entire rear end.

 

It is not normal for the gear box to leak. Being a mechanic, you should know that. If I were you, I would take my truck to another dealer. You need to address this issue forthwith.

 

I knew that it wasnt normal for the cover leak. And thats why I was concerned. But the dealer however was not as concerned as I was about the problem. And I suppose the responsible thing would be to take my truck into another dealer and address the issue with them. Hopefully they will take me more seriously.

 

The cover does not use a traditional gasket - it uses a bead of specific silicone sealer applied in a specific manner. Find a dealer who will fix it right instead of flipping you off. If you want to do it yourself, buy the sealer from Ford and research the exact procedure in the shop manual - there are old threads here somewhere addressing both the part # for the sealer and the procedure.

If you do it yourself, pick up a 4 oz bottle of friction modifier at the dealer, and get some synthetic 75W140 gear lube.