My 2006 F150 just turned over 31,000 miles. During the most recent oil change at the local Ford dealership they found the rear end pinion seal leaking and replaced it - topped up the oil. A few weeks later I noticed a "humming" noise or light roar coming from the rear end. I took it in and paid the $85 fee for problem analysis and was told that when the oil level dropped because of the leaking pinion seal that it probably initiated a little wear but that everything was well within specs. They then told me that F150's are notorious for rear end noise and that trying to rebuild it would probably only make the noise worse. The only solution (they said) was to replace with a new one to the tune of $2,700. My question was why replace it if it is within specs and is typical of F150's with only 30,000 miles on them. They assured me that everything else checked out just fine and that they could find nothing wrong that would cause any problems. This week I have noticed that an additional "thrashing" noise is now coming from under my truck along with the humming. The noises increase with speed and decrease when I slow down. The humming seems to get louder when going down hill and I let off the gas and seems quieter when pulling up long hills. This afternoon the weather was cool for the first time in awhile and I drove home with the windows open and was surpised at how loud the "thrashing" noise seemed to be. When I got home and put the truck into reverse to back into my carport I noticed a "squeak" sound as the truck started to move. Other than the noise the truck performs normally. Any ideas? Thanks!

 

is the seal still leaking??? my truck has a slow leak on that seal. I drove mine for like a month, prolly close to dry. added fluid now my truck feels like it is draggin some thing, but like you said other wise it seems to run fine

get a second opinion for the noises.

 

Mechanics at dealerships are very much like private shop mechanics in that some are great, some not so much. Difference ios those in private shops who aren't so good suffer losses in customers while dealer shops stay busy.

My guess is the mechanic that replaced the pinion seal removed everything necessary, replaced the seal, and simply retorqued the nut when putting her back together and likely added a bit of crush to the crush sleeve thus eliminating some some of the bearing clearance that existed before he took the nut and yoke off.

Or maybe he did remove axles and carrier and reset the whole rear end up .... and he missed the sweet spot. Either way, it ain't as right as it was when you took it in. Telling you the only cure is a total replacement is much akin to telling you they don't have a giood mechanic trhat knows rear end set up.

My '07 with 9.75 rear doesn't "hum".

 

I know this prolly isn't it but are your u joints loose? Mine made an awful racket when they got loose. The rear end could be in spec and the u joints hollering. 30k is low for problems tho...

 

Nope - I thought of that and checked it first. Seal seems to be doing just right and the rear end fluid if full. I've had several seconds tell me it's probably the U joints. Guess I need to check this next - just need to find out the best way to do so. I'm not paying another $85 to the local dealer.

 

Agreed - the local guys do pretty well with the basics - I'm not so convinced with more challenging diagnostics. I didn't think about the reassembly issues you mentioned - might be something to check as well.

 

I'm going to jack her up tomorrow - put the tranny in neutral and do some rotating of the drive shaft to see if the u joints make any noise or appear to be loose. That is my next suspicion. I know that 30K is low mileage for u joint problems but I relocated a year ago and towed a very heavy trailer 1000 miles over mountains. Someone told me this week that the mileage isn't as important as the time with factory u joints and this is an '06. We'll see when I get the jack stands in place.

 

If the yoke nut was overtightened and the crush sleeve was affected, what is the cure? Will it cause premature failure of the rear end? I'm not familiar enough with rear ends to know what the "crush" issue involves. Thanks!

 

Well, I don't mean to worry you, I'm just a guy 6-700 miles away probably.
If the mechanic did do what I said it almost sounded like (and it may be he didn't, I can't say for sure, but I know it happens), then by retorquing the nut whith an already partially crushed crush sleeve, if the sleeve "gave" any more, if it "crushed" further by the torque being applied, then the original running clearence that was allowed when the pinion gear was installed and bearing preload was removed and the pinionm bearings are running with inadequate clearances. They'll get hot, maybe someday turn blue and soften even, they will fail in time.

If it were mine, and if I suspected it, I would first go to the dealership and try to talk with the mechanic and NOT in an accusatory manner ..... but as a concerned owner looking to cure my truck. We don't know what he did, it's just maybe "suspect" at this point. Maybe he'll tell you how he did it or maybe they will take another look at it?

I've seen guys write on here that what I described was the way they did it, but I know first hand that removing a long torqued pinion nut and then retorquing it after a seal replacement will sometimes further crush the sleeve between those two bearing's inner races. If that same nut is reinstalled and tightened past the point from where it was before, the sleeve yielded (as you can bet the pinion gear's stem didn't stretch). I learned it 40 plus years ago, it cost me a lot at a time when I was working for $2.10 an hour.

The only way to know for sure is to get it on a lift, pull the axles, pull the carrier and ring gear out, and check bearing preload with just a pinion gear in the housing. If tight, it will take a nw crush sleeve .... and seal ..... and maybe a pair of pinion bearings to fix it, then reinstall carrier with ring gear and reset backlash (and then I'ld maybe even check the tooth pattern with yellow lead, etc) and reinstalling the axles and a cover gasket or new sealant and gear lube.

Maybe you have a friend with a shop who knows rears? Ask him to take a look with the drive shaft removed, he'll know what to feel for.