Just bought a used F150, 5.4, 3.73 limited slip. 70,000 miles. Anyway noticed some oil on the rear diff. Appears to be coming out from where the drive shaft goes in, and blowing oil back on the diff when going down the road. Any ideas? Is it an easy fix? Thanks in advance. I had an 02 F150 before all my one tons. They have sure come a long way since then, nice truck! Thanks, Levi

 

How bad is it leaking?I'd remove the filler plug and check the fluid level.If it isn't low than it's nothing too urgent.If there is a noticable loss of fluid I would find a competant shop to change it.Maybe even the Ford dealer if they don't charge an arm and a leg.The changing of the seal is easy enough but it can be tricky getting the correct preload on the pinion nut.A guy on another F150 forum had a shop change his pinion seal and they got the preload wrong. 4k miles later the pinion bearing went bad.

 

check the fliud level first, then check for play where the yoke goes into the front of the differential, if there is any slop, the pinion bearing is probably bad and needs to be replaced right away. If the yoke is tight and the fluid level is full then you should be ok for awhile, just keep an eye on it. Alot of times leaks like these look worse than they really are because wind blows the oil all over and then road grime sticks to it and makes it look really bad.

 

We're taking it in on Friday. That is exactly what it looks like, and would confirm my suspecion. Thanks for the info. Levi