I have a 1999 f-150 automatic, v-8, 2-wheel drive that has developed in a noise on the passenger side in the rear drive train area, i just replaced the tires, so that is ok, tranny does not slip, and was wondering if the problem is in the differential, it is a winding noise that is heard only when I apply load to the engine (stepping on the gas pedal) sounds like a wine but is absent when I am coasting? any clues to what is causing this would be helpful. thanks

 

could be that..or...outside axle bearing...or...carrier bearings.....or pinion bearing...or...all of the above caused by the first question..600 bucks and up...it will only get louder,then quiet

 

Usually, a noise on acceleration is an inner pinion cup & cone. A noise on de-acceleration is usually an outer pinion cone & cup. Noise all the time is usually a diff. side bearing or an axle bearing.

If You find a bad bearing in your diff., I would reccomend changing all the bearings, crush sleeve, pinion seal & axle seals & pinion nut (minimum).

 

For us dimwits, please explain inner and outter pinion bearings.

By inner do you mean the bigger one that is pressed on the pinion???

 

The outer brg. is the one immediately behind the yoke & seal. The inner brg. is farther inside pressed on the pinion. A collapsible spacer, or crush sleeve is located between the inner & outer pinion brg's. (cup's & cones).

 

I did not change the pressed on bearing on the pinion, only the one behind the yoke, because the pressed on bearing looked really good in terms of wear. There was a slight scratch on one roller, but I did not think it would cause a problem.

Would it help with the whine to increase the crush on the spacer...ie/ tighten things up??

 

The only correct way to examine a tapered brg. on the pinion or diff. side is to remove it, clean it & examine it with a bright light on the inner race portion. The brg. may look excellent from the outside portion; however, when you look at the inner race, it may have spalling or pitting that has occured. Pitting or spalling will lead to noise, which will result in a brg. failure. Many brg. problems are mis-diagnoised because people only look at the outside portion of a tapered brg.

If You torque the pinion nut tighter on a used brg.--spalling will probably occur. If You have previously had the yoke off of your diff., maybe you over-torqued the used (inner) brg.

I did this to one of my own diff's. (and I have rebuilt hundreds of diff's.). I was in a hurry and over-torqued used pinion brg's. I knew when I pulled on the street (after re-tightning the old pinion brg's, that I had a problem). I could hear a low speed "scraping" noise. The noise continued to get worse (on acceleration) until there was a very loud hum whenever I touched the accelerator. I drove the vehicle for another 6 months before rebuilding the diff. When I removed the diff., pinion brg. spalling had occured. There were millions of tiny, "shiney" particles everywhere. Brake parts cleaner would not even remove all of the metal particles from the axle housing. I had to used a high pressure washer to blast the axle housing clean.

Whenever repairing a diff., I reccomend using all new brg's.. You might be able to reuse axle brg's., but, replace the axle seals. Diff. brg. kit# for an 8.8" rear axle is RA311 & can usually be ordered thru any local auto parts jobber. RA311 will not have axle seals (national# 8835S) or axle brg's. (BCA# 6408) in it.