My '97 F150 seems to have a humming noise coming from the rearend when turning right. I changed the fluid about 2 months ago and it didn't seem to help. I'm going to try an add another 4 oz of friction modifier and see if that helps. I'm tinking that the LS clutches are worn out. Am I barking up the wrong tree? Can a driveway mech change out the clutches or do you need a differential expert (i.e dial indicator, preloads etc...)

 

If you have the correct ratio in there now (friction modifier vs gear oil) then adding more friction modifier will make it slip more.

Rebuilding a stock locker can be done. The backlash shouldn't change since all you're doing is rebuilding it. However, it doesn't hurt to check it anyway if you have access to a dial indicator. One thing I would recommend is to slide both axles out, completely, and punch a rag though each side with a broom stick. This would also be a good time to check the bearings as well.

 

Thanks for the reply Blurry. I changed the axles bearings at the same time I did the fluid. I thought that the bearings were the problem, obviously I was wrong about that. Is the noise I'm hearing a symptom that you would expect to have from a LS going bad, or is there some other place I should be looking.

 

I personally haven't experienced that problem with worn LSD, but that's not to say it doesn't happen. Do a good visual of the rear suspension components before tearing into the rear end.
My stock traction lock had broken/worn friction plates at the bottom of the housing when I pulled the cover, but it never made a peep. The Auburn I had after that just blew to pieces and it never made any noise either.