Differential whine question

[apollard]

Not for a mustang, but a diff is a diff -

'04 Dodge truck (yes, I know, that's my problem)

The diff whines something fierce when moving, and has been getting worse for a while now (sort of crept up on me). Starts around 10 mph as sort of a growling, then becomes a whine, and raises in pitch as speed increases. Between 30-65 or so, it is loud - hard to understand voices on the radio loud. About 70 it seems to become quieter, likely because it's getting above the hearing range.

Does not change when accel / decell / coast, just with speed. Does not change with turns, no matter how sharp. Does not change with load (pulling 7k lbs even).

Jacked it up, and the sound is still there (ie, not tires), and is coming from the diff, not the wheel bearings. Ring gear backlash is `10 thou (range is 5-8 thou).

Read all the FAQs I could find, and none talk about a noise that changes only with speed. All say ring gear backlsh should change with load / accel/ decel. They also say a couple of thou won't cause loud whining.

So, I'm thinking carrier bushings, as pinion bushings and gear noise apparently should change with loading. But, none of the sources I found said anything about this - what say the gurus here?

[Fast68back]

Have you ever changed the fluid? I dont know why, but I do know its on the service item list at selected intervals.

[Mach1Rider]

Carrier taper bearing or race is going out. prob why no change on accel or decell, load or corners.
But would account for backlash change.

[apollard]

Fluid is Mobil 1 synthetic 75W140, changed every 20k miles (I tow a lot at high speed).

I'm thinking bearings also, but know only a little about diffs.

[camachinist]

How many miles on the truck?

Have you isolated with a stethoscope with it on stands and running? Bearing noises are pretty easy to isolate that way.

Do you tow overloaded (over GCWR)?

[daveSanborn]

Coincidentally my '04 Dodge truck is down right now also.  Are you 100% positive it's the rearend and not the front wheel bearings?  My drivers side front wheel bearing is binding causing a very audible whine that only gets worse with more speed.  Acceleration, deceleration, coasting, braking, cornering had no effect on the pitch/frequency of the noise.  At first I assumed it was transmission or rearend related, but then I brought it to my alignment shop thinking it might be out of align and after looking at the tires my buddy suggested front wheel bearings.  Sure enough, I went home and jacked up the frontend.  Giving the passenger tire a spin it rotated approx. 6-7 times.... same force applied to the drivers side resulted in less than one complete revolution.... and it doesn't sound too good either.  The truck sits parked waiting for me to fix it.  New wheel bearing assembly is in stock at the local dealership @ $135.  The truck just turned over 60,000 miles.  POS.

[apollard]

How many miles on the truck?

Have you isolated with a stethoscope with it on stands and running? Bearing noises are pretty easy to isolate that way.

Do you tow overloaded (over GCWR)?

95,000 on the meter. I have not used a stethoscope, as 1) don't have one, and didn't think of the pipe trick at the time, and 2) if one bearing is bad, it likely damaged them all (metal filings). But, I think I'll do it now anyway just for secondary confirmation before ordering parts.

Have never towed overloaded, although I do tow close to the GCWR (about 12-1500 lbs under). Also, most of it's life it spent towing at 1/2 the GCWR, just the last 6 months or so that I've been close.

Are you 100% positive it's the rearend and not the front wheel bearings? ... The truck just turned over 60,000 miles.  POS.

Positive - it makes the noise with the rear end on jack stands and the front wheels stationary. More importantly, BTDT on the front wheel bearing, and at 65,000.

POS is right, mine has several other less troublesome issues now. Overall, the quality sucks for a truck that has been taken care of it's whole life. First reason my next truck will not be a Dodge. Second reason:

[68EFIvert]

I have a similar problem with my Sequoia now.  It has been there for a few weeks.  I have had guys tell me it was tire noise (new tire store), wheel bearings (old tire store) and another that could not find the problem.  The wheel bearings seem like they are in good shape and do not have any play.  I replaced the tires but the noise stayed.  I think I will take mine to the dealer for diagnostics and then  take it from there.  

[apollard]

Well, I fionally tore into it, and the problem was the friont pinion bearing. One roller was trashed - sprisingly, all the others looked good, even though tha one had been trowing metal bits off, and the race was damaged. Also, it did not change at all with accel / cruise / coast like all the FAQs said. So much for the advice of experts.

Everything else looked good, but I changed all the bearings. Gear setup was easy. BUT, that dang crush collar is a b*tch! 210 ft-lbs is supposed to do it, but I ended up using a jack to push the end of the breaker bar until I got the correct preload. I have no idea how much torque it took, but I finally got the correct preload. Took almost as long to do this as it took to disassemble & clean. It would be much easier out of the car, but taking it out, reinstalling and bleeding the brakes would probably have been a wash on time.

I had fogotten how quiet the track could be on the road. This thing had been eating itself longer than I had thought - the noise creeps up on you.

On the plus side, I'm set and armed with experience when I change the Stang to 3.55s.