Help diagnosing differential problem

Reply Subscribe

Thread Tools

Search this Thread

Nov 16, 2019 | 05:19 AM

traildad

Thread Starter

Mountain Pass

Joined: Apr 2013

Posts: 101

Likes: 4

Help diagnosing differential problem

I have a original 3:55 limited slip 9.75 diff in my 02 f150 with 300,000 miles. It developed a pinion leak so I figured I could change the seal to fix it. I decided to also replace the original u joints thinking they might have caused the leak. The pinion nut seemed to be much looser that I would expect considering the torque applied to crush the sleeve. I figured I should inspect the bearing but I can’t get it out. Now I am wondering if the stuck bearing is a sign that I have bigger problems causing the leak. I haven’t heard it making noise though. Should I just rebuild the rear end? A recent list of repairs is starting to grow and I’m getting nervous about throwing good money after bad. If I have it rebuilt what should I check to help figure out if the shop is competent to do the job? Is there a good source for parts that aren’t cheap junk or expensive overkill for this old truck? Thanks for the help.

Nov 16, 2019 | 08:41 AM

alloro

Fleet Owner

Joined: Apr 2008

Posts: 24,318

Likes: 5,128

From: 0,0,1

Quote:

Originally Posted by traildad

I have a original 3:55 limited slip 9.75 diff in my 02 f150 with 300,000 miles. It developed a pinion leak so I figured I could change the seal to fix it.

Here is the procedure to change the pinion seal.

Attached Images

2002 F150 Pinion Seal.pdf (168.9 KB, 93 views)

Nov 16, 2019 | 10:27 AM

traildad

Thread Starter

Mountain Pass

Joined: Apr 2013

Posts: 101

Likes: 4

Quote:

Originally Posted by alloro

Here is the procedure to change the pinion seal.

Thanks. Unfortunately it is in front of my house with the drive shaft out. Pinion nut and seal removed so it is too late to follow those instructions. I am now trying to decide if I need to rebuild the rear end based on the stuck bearing, loose pinion nut and oil leak, or simply because it has 300,000 miles. I hesitate to just slap it back together and guess at the preload setting.

Nov 16, 2019 | 11:43 AM

steve(ill)

Hotshot

Joined: Jul 2005

Posts: 11,931

Likes: 180

If the nut was loose and the bearing is dragging / stuck , then you need to replace the bearings... You will have to remove the back cover , pull the axle half shafts, pull the bevel gear and shaft... then the pinion goes out the back... Your probably in too deep right now. Might need some help.