I have an 01' 4.6 125K and I have replaced the pinion bearings (inner & outer) in the diff housing twice now and I am still having them wear. I found the race was pitted and the bearing would wear after 2 months. I removed the axles and diff and replaced the bearings again and a couple of monthe later, the noise is back. I am at the point of finding another 8.8 rear end and trying that out. I am running Royal Purple 75 / 140 Diff oil. Any help would be greatly appreciated.

 

Were u getting a whining noise from your rear end? You might have excessive backlash and it's wearing the bearings and races prematurely. Try checking backlash after you get it rebuilt. Did you use the special tool to set the shim for the pinion depth? there is a TSB out for replacement of the pinion and ring gears for excessive noise at highway speeds. So bearing replacement alone may not fix it...

 

Thanks for the info. I actually had my mechanic do it for me and he said the shims looked good. I am not sure if used the tool to check for backlash or pinion depth. I will ask or find another person who can assemble it properly. All I know is it is making a whining noise and when I looked at the race and bearings, the race was pitted and worn within a month or two. Again, thank you for the support.

 

I just rebuilt my 8.8 / 3:31 rear on my 02 f150. Ford manuals recommends 4-6 inch pound resistance in spinning an unloaded pinion (no ring gear installed yet). If the pinion nut is too tight you will wear the pinion bearing out in no time at all. Tighten the pinion nut down until you have that resistance. A little too tight is ok but it can't be tightened down like we used to do them...The older pinions required that we tighten and test with Prussian blue over and over until we got the right contact between ring gear and pinion. That isn't the case with today's Ford light duty trucks from what I understand.