Hi. This question is pertaining to my '99 F150 2wd 4.6 litre auto tranny.
It has about 145k miles on it, and the rear axle has a howling noise (not very loud, but it's there). It starts howling when the speed of the vehicle reaches about 35 MPH, and only under acceleration, when coasting, the howling goes away. The frequency of the noise increases as the vehicle speed increases, but doesent seem to be as pronounced at hiway speed, as in city driving, I'm guessing because at hiway speeds, the frequency is too high, so it's not heard as easily.
Anyway, I have seen in other posts that this might be the inner pinion bearing at fault. Is there any way to replace this bearing without removing the differential case from the rear housing? And how difficult is it to replace this bearing or bearings? Could this be wear on the ring or pinion gear causing the noise?
If any of you that has been though this before could give me a little advise, I would appriciate it.
Thank you!

 

Sounds like the Pinion Bearing most likely, just did mine in my ’95 f-150 last week.
It is not hard to replace the pinion bearings if you use the same Ring and Pinion.
Just put all of the shims back where they came out from. Mark left and right, they will be
different.

You need to make a Companion Flange holder out of ¼” plate about 3 feet long and drill three
½” holes in it. I cut mine out with my cutting torch.

You will also need some tools if you do not already have them.

¼” beam type torque wrench, 0-50 inch pounds . for setting the pinion preload.
¾” ratchet with about a 4 ft pipe to fit it for the pinion nut.
¼” 8mm 6 point socket and hinge wrench for removing the lock bolt.
Dead blow hammer for driving the Differential back in.
½” torque wrench.
12 Ton Press for pressing bearings off and on.
Bearing seperator for the press.
And other common tools.

This all worked for me, but on guarantees.

Also get a manual on how to do this as I may have left out some items or steps.

My routine, the record readings were for my records, you can skip them if you are going back
With the same shims and no body has been in there since FORD.

1. Jack up truck
2. Take tires and drums off
3. Check wheel berg. By trying to move flanges up & down
4. Run engine in drive a monitor rear end with stethoscope
5. Remove drive shaft from Companion flange
6. Check pre-load and record
7 ½ to 10 + also catches to 15 in lb
7. Take brakes off
8. Loosen back cover and drain rear end
9. Take cover off
10. Remove Axles
11. Check backlash and record
.010
12. Check pre-load and record
5 to 10
13. Check and record case runout
.0035
14. Pull ring gear and record shims pos. and record thickness
Left = .259 Right = .288 with bevel to outside
15. Check pinion depth and record
2.83 – 2.844 -.25 (2.605 – 2.594)
16. Mark Companion Flange Pos. to Pinion
17. Remove pinion noting shim pos. and record thickness.
.0024
18. Record thickness of collapsible Spacer
New = .510 Old (USED) = .445
19. Push paper towels through tubs and clean center housing
20. Check pinion races for ware and replace if bad
21. Reinstall pinion, match Flange Pos.
22. Set pre-load New Berg. 16-29 lb-in, Used Berg. 8-14 lb-in
23. Replace carrier bergs. and races
24. Reinstall ring gear.
25. Check case runout, max 0.003 inch
26. Check back-lash 0.008-0.015 inch ([0.012-0.015 inch] Preferred)
27. Reinstall axles

28. Reinstall spider gears
29. Reinstall cover
30. Fill unit and run in drive
31. OK, turn off engine, do not touch brakes
32. Reinstall brakes
33. Reinstall drums and wheels
34. Lower truck onto wheels and test drive