Anyone know what this rear axle moan (or humm) is? I heard it was a fairly common factory defect on 2002 F150s. It is a 4.6L, so the rearend is 8.8. The moan is constant, and gets louder with increased spead, and is louder with gase than coasting. It started around 15 or 20K miles and I have 65K now.

Is carrier gears? It doesn not sound like a pinion bearing, pinion gear or ring gear.

I would kinda like to know what it is before I start taking the rear diif apart and investigating myself. Knowing this might save me some time and effort. My warranty has expired.

 

Disclaimer: These are very general ways to tell what noise is what. Unfortunately, as I can't hear what you're hearing, I'll make a few shots in the dark as to what exactly you're hearing.

Most bearing noises are pretty consistent, either they're there or they aren't. If you're hearing a noise on accel, it'll probably take a new ring and pinion to square it away.

At speed, shift the trans into neutral and see if the noise goes away. If so, start thinking ring and pinion again. If not, you've got a/an bearing(s) going south. I've never had one that had the spider gears in the carrier go bad, it took new ring and pinions to make them quiet again.

 

nyroc, I have a 2000 F150, 5.4 with the 3.55 LS and just over 65K miles. About 2 weeks ago I noticed a slight hum from the rear end. At first I thought I had a tire going bad. I don't hear any hum until I go over 20 MPH, then it's all the time whether I'm accelerating, coasting or slowing down. It got progressively worse so I stopped by Ford Friday and had the service manager drive it. Not good news, he said I had bearings (not wheel) going bad in the diff and he was surprised that as bad as it was they hadn't gone out yet. So Monday I have to drop it off for them to tear apart and see what all needs replaced. He recommended I not drive it because if the bearings go out it usually takes out the housing ($2000) with them. Estimate is $600-800 for the repair.
Before he drove it he told me they had just had a Ford specialist there looking at another F150 that had a hum only on acceleration. Apparently, the ring and pinion were bad and needed to be replaced. Problem is he said was whoever builds the ring and pinion for Ford hasn't replaced the dies <sp?> in sometime and they produce ring and pinions that show the same hum after only 3 or 4k miles after replacement. He said Ford is working on a fix, it's just no here yet.
I have towed 5000 lbs (tractor and trailer) about 1000 miles total on separate occasions and just 3 weeks ago I towed my 4000lb TT to Florida and back (about 400 miles total). Then just last weekend I bought a 27' TT (6200 lb dry weight) and towed it about 50 miles. It had 1000 lbs of water in it that the dealer had left in it checking the systems and I didn't realize it was still in there until I got home
I had a leaky pinion seal at 6K miles and that's the only trouble I have had with the truck. About 10K ago I added another bottle of friction modifier because of a little slipping in the rear end. Now I'm wondering if maybe that's what did my bearings in?
So long story short, if it's the same hum, it's bad news!

 

Also, if anyone would care to comment, if the ring and pinion require replacing would it be worth it going to a 3.73? My truck has the stock 17" tires and I'm wondering if the lower gears would be that much of a benefit when I tow my new TT?

 

if you have to pay for it out of your pocket, shouldn't you go to an aftermarket company instead and have the Ford dealer or a performance shop put those in instead of using the Ford part again ?
just wondering why you wouldn't check out Richmond Gears or someone like that, or don't they make them for these trucks?

for towing i would go with the 3:73 gears. that's what i have with my 17" rims.

 

Ford has been telling customers that they're working on a 9.75" whine solution for over 5 years. There is very little difference between 3.55 and 3.73 performance. If Ford is doing the work and would be willing to install a set of 3.73s, let them. If you buy your own gears, you should install 4.10s for towing and only a few companies offer this for a 9.75" rear end. Ford Performance Products is not one of them, they stopped several years ago. U.S. Gear, Precision Gear, and Motive are higher quality sets.

 

Thanks, but it turned out to be carrier bearings and the ring and pinion was fine. Still cost $640.00 for all the bearings to be replaced

 

Your problem sounds somewhat similar to mine. I had my rear pinion seal replaced at 37,000 miles and ever since have had nothing but grief. Prior to replacing the seal, my truck ran flawlessly. Soon after the intial replacement, I noticed a grinding noise from the rear end. The dealer has since replaced the rear pinion seal three more times, the rear pinion bearing, and the ring and pinion itself. I have a hum from the rear at 40-45 mph, and at 50-55 mph. The hum is more evident when pulling my 3,000 pound boat, but still occurs at the same speeds. In addition, I've noticed a constant hum from what sounds like the right front at 60-65 mph. This started after the rear end work was completed. Could this be related? The dealer says my tires and wheel bearings are fine. Fortunately, my dealer has picked up all the costs for the repairs. They even gave me an extended warranty until Ford comes up with a "fix." Is Ford really working on a solution to this problem, or are they just stalling? My truck now has 63,000 miles and continues to run very well with the exception of the above noted problems. I plan on keeping the truck for many years to come and desperately want to get this problem taken care of once and for all. Any suggestions are greatly appreciated.