About a week ago I began to notice a slight jerk when backing out of the garage. Trans shifted into reverse ok, jerk happened after backing out about 3 feet. Then yesterday I was about 20 feet out and it jerked so hard I thought I had hit something. No problem going forward and after driving 7 miles and the truck was warmed up it wouldn't do the jerk when backing up. I have 3.73 ratio dif.
Any ideas, I hope it could be simple as a fluid change, 140k on truck and I don't remember ever changing the fluid.

Thanks, Walt

 

It would not cost alot to pull the cover and drain the oil.Inspect the gears and all.Fill it up with fresh oil and the friction modifier and try it.

Welcome to guzzle's Rear Differential Maintenance Web Page

http://www.guzzle7pt3.com/fdiff.php

 

X2 change the fluid ad inspect the gears to see if there is anything obvious wrong

 

Thanks for the advice robs01f250 and riverrat41, thought I should get back to you on the real problem.
Both L/S & R/S rear brake pads had broke free of the plates they were bonded to. They were the high dime NAPA Ceramic pads, I only had 25,000 miles on them but they were installed 4 years ago so NAPA would'nt give me a break (two year warranty).
No more NAPA CRAPA for me.

 

At least it wasn't the differential.

Did you end up pulling the cover and replacing the fluid?

 

It's a good thing you figured it out. Brakes are a vital part of any vehicle

 

I had the same issue w/ a set of Napa front pads - scared the crap outta me. I'd put on the brakes and the truck turned left - the outer pad on the driver's side had broken into pcs. They were about a year old when it happened. Same deal - no warranty. Bought wagner pads to replace them

 

I know most guys have their "favorite" brand of aftermarket pads... I've found the Ford OEM HD pads are GREAT. Not the motorcraft units, ask for the ones that are OEM HD in the plain ole brown box with just a Ford part number. All I used on all the trucks I worked with. No problems.

 

Thanks again guy's, I have not done the fluid change in the diff. yet, but it's on for next week.