troubleshooting front end noise?

I think I have what is front end axle noise. It is a higher pitched noise that goes back and forth between two frequencies about twice a second. It doesn't sound like tire noise that I am used to with the BFG tires. So far I have spent some time running on a jack stands and swapping some parts with spares to try and change the noise. The noise starts around 20MPH and seems worse on acceleration or coasting. At 40MPH its very clear. Engine speed or transmission gear does not vary the noise. Applying the brakes or deceleration don't really change it either. There is absolutely no vibration - it is only a noise

- Tried removing front driveshaft - no difference
- Tried swapping each wheel bearing with a spare, and each tire with a spare - no difference
- Inspected front and rear brakes; found rear left adjuster may have been grooving the brake drum. No change after repair
- Ran on jack stands up to 40MPH in 2wd, 4wd, with front and rear driveshafts alternately removed and both removed - don't really hear it! What I do hear is a god awful noise from the transmission when it shifts into 2nd or 3rd gear with driveshaft. No driveshaft, purrs like a kitten. On the road it doesn't sound anything like the noise. Put a pipe to the cover of each differential to listen and only hear a low humming noise like everything is fine. Both front and rear sound the same.
- Remove accessory belt and couldn't find anything suspect
- Removed auxiliary fan which squeaks when pushed - no change
- Front pinion nut is tight, not leaking

I first thought I heard the noise after I changed the carrier bearings/axle seals but my memory could be off on that. I was coming back from vacation including some light wheeling with a friend. I didn't touch the pinion during the repair.

Any ideas on how I can determine the cause of this noise?

This help?

6 part article.

http://www.dodgeram.org/tech/repair/axle/diagnosis/page1.html

Thanks.

On Friday night I concluded that it is probably gear whine. The gears aren't really setup any differently than they were back in January when this axle went in which is why I didn't suspect that first. The pinion depth appears incorrect. I could be that the thinner gear oil after the axle seals simply makes the noise audible. I had been running 80w-140 in it. I am going to work the pinion depth. If all else fails, I'll replace the axle with a spare.

I thought it was interesting that neither the original axle or the replacement housing had any pinion shims under the bearing cup. No changes to the slinger were involved. The baffle and pinion bearings were changed. Preload on the bearings was set properly.

the factory doesn't put shims under the cup. It is an acceptable method though.

It's highly likely you will not get rid of the whine as once the gearset has achieved break-in, any other set-up other than the exact one it was in when it hardened will whine.... some louder than others.

Thanks Don. I'll give it a try if nothing else for getting more experience. This was the starting pattern before I disassembled:

(These are factory 3.55)

I've been considering replacing with 3.73 for the 30" tires I'm using but I'm not sure it would be worth it.

Any correlation to the way the carrier bearing races looked?

non Ring gear side:



Ring gear side:

I'd be very suspect of that housing. I must admit I've never seen a pattern like that.

Go 4.10s if you decide to gear. Or deeper if you plan to go bigger soon. Going above 3.55s, you have to run a new carrier for the split in the 30 anyways. Consider maybe looking for a 4-cyl D30, as it will most likely have 4.10s as 4.56s were VERY rare.

This is a good read from Timken.
Bearing Damage Analysis Reference Guide



In your case, look at figure 36. I have seen such failures in Dana axles but not as severe as yours. I see fig 36 and fig 29 most commonly in the D35, Aluminum D44s and the D30. They are terribly abused by their owners and and can't handle lack of maintenance.

Thanks Don. Those particular bearings had 6,000-8,000 miles on them so I'm thinking it is more of a deflection issue mentioned than maintenance. The wear pattern starts almost immediately as I've found by changing axle seals twice now and doing the bearings at the same time. I did get rid of the seal leaks by using genuine Spicer seals and smearing Vaseline (instead of gear oil) all over the shafts and seals. I am hoping the deflection could be related to pinion depth and if I correct one I may correct both. But I don't know if that's just wishful thinking and I should change the axle. Tonight I removed the .020" baffle and put in .032" worth of pinion depth shims. Rather than go through the effort of using pinion preload shims, I snugged it up so there was about 5 in-lbs of drag. I read this was acceptable during setup. The pattern changed to:





Tomorrow I'll try reducing the pinion depth shims by .004 or .006?

Here's the pattern with .028" in lieu of the baffle behind the outer pinion bearing:





I was surprised at the difference +./- .002". At .030" it looked a little too deep and at .026" it looked too shallow. Backlash here is at .009" so I need to adjust that.

nothing wrong with .009". Especially with that pattern.. leave it alone.

I put it all back together and the whine persists. What is strange to me still is that it only makes noise going down the road, not with the tires spinning in the air. I guess I'll swap the axle.

I found that the problem is actually the rear axle. Then I took it apart and found out why: