A long description. Have a 05 F150 w/335 LS rear differential with 215K miles. Rear diff fluid has been changed at 60K intervals pretty much since new. Last fall I replaced the very aggressive tires the PO had put on the truck with an all season radial. As soon as I did that I heard the howling in the rear that the old tires had been covering up. The PO put them on just before I bought it 40K miles ago. I diff changed fluid shortly after putting on the new tires. Rear was quiet for a while then the howl came back. Last month I had the diff serviced again using Lucas 75W-140 and Motorcraft FM just as I did last fall. It was quiet for 2 weeks then the howl came back again. The howl is heard going up a mountain and coasting down a mountain. If I give it a little gas then the howl goes away. So the howl is when there's pressure on the rear end. My question is it possibly bearings or the R&P gear set? I'll need to have the work done by an independent shop and just trying to get an idea of cost.
Any clarity or assistance would be greatly appreciated.

 

If it's noisy under accel / decel and quiet in the float, my first suspect is the pinion bearings. Specifically the front since its the furthest from the oil, although you'd obviously do both while you have it apart.

 

Any other advice? I need to have this done soon before we move. I have a mechanic here that I trust. We're moving 4 1/2 hours away to an adjacent state. The estimates are $750 to do the pinion bearings, seals etc. and to do a full overhaul is $1200. Labor for a complete rebuild is 7 hours. What does everyone think? Is it most likely a pinion bearing causing the howl? I have a lot of confidence in recommendations here over the years.
TIA

 

Bearings are toast. It happens. You might be able to do the job on your own but you need to have the service manual. Lots of things you could mess up doing a bearing replacement.

 

I don't have the time to do it on my own. Since they need to pull the gear set to do the pinion bearings I think it's best to do the whole rebuild. Can't afford it but can't afford not to.

 

 

I recently had my truck in the shop due to some odd vibration issues in the driveline. It was fine under 70, no vibe with load. On coast down a mountain, it would vibe like a banshee. I looked at the DS and u-joint, from what I could tell these were good. So, I went off to a local 4x4 shop that said they can diag drive shafts/angles and such, thinking maybe the issue was the shaft, or something in the transfer case. They had the truck like 4 days, then noted the sealer on my rear diff was fresh. They popped the cover off and that was when they noted the other shop who installed my gears must be retarded. The shims and carrier bearings were smashed, and the backlash was at 0.0002". They re-set the gears, I cannot tell when I am going over 70, in fact, coming down a mountain at 90 its as smooth as glass! Additionally, the truck has more power with the rear end properly setup!

My money is your diff needs to be re-built. They charged be about $719 for this, it was a major kit and then labor. At the same time when it is re-built, I would suggest a new spring and new frictions for the rear end.

 

My '07 Supercrew 4X4 is not making any howling noise as yet that I can hear ,but when making turns I am starting to hear and feel a clunking sound. Does not feel like any u-joint issues I've had in the past. I'm guessing something in the rear axle possibly the differential itself. It is the 9.75 rear axle,3.55 gears and L/S.

 

I had a howling in my Ranger torsen rear end. Drove it like that for over a year, knowing it would let go someday. It did. Wish I could find the pics, it ate itself up pretty good.
I just picked up an entire used rear axle, and swapped the whole thing out. Got it for $500.

 

Mine 2004 at about 124000 miles has had more of a rear end whine than a howl at around 45 mph. I had a "mechanic" ride with me and listen. He was a Ford hater I think. He said the rear end was shot. At any rate that was at 80000 miles. The sound has not changed. I will continue to drive it until it sounds different. I also replaced the fluid and put in the Ford anti slip juice around that 80000 mark. I used Royal Purple.