Hi, I have a 89 F150, 4.9 L, with 5 speed manual. The u-joints are new. When I'm driving and upshift and let the clutch out, the differential clunks. The diff. makes no noise, like humming, or anything, just the clunk when the clutch engages. The truck has 104,000 miles, and has pulled a small boat over the years. Someone told me there could be shims put in there to get rid of the clunk (obviously a lot of play). Is there such a thing, or is this an expensive proposition? Thanks

 

You'll have to open it up and check for pinion play, carrier play, contact pattern, and back-lash measurement.

 

Pull the driveshaft off. Grab the pinion and wiggle. If it has any play, you need a full rebuild. If not, pop the cover off and check the backlash. It should be between .006 - .010. If its not, a shim kit is $20 on Rockauto.

 

Haha my rear diff has a pretty good amount of play. I can turn it pretty good

 

Thanks for the information. since I'm not familiar with the diff, I should have it checked by a shop. While the play many not be a risk at the moment, I can stand to hear that clank when I shift. I doubt that it being low on oil would do that, right? I would think it would be whining or rumbling with low oil, right? Thanks guys