Gear Noise from Transfer...Bearing? (1 Viewer)

[CaptHamster]

Hey all

Over the past few months, I have been getting a progressively louder gear noise coming from the transfer case over ~20MPH...Here's some more info:

1.) TCase work done by a local shop approx 5 years ago (overhaul w/new shims, bearings, races and seals)
2.) Gear noise only when under load, no noise when off the gas; seems louder under light load (coasting w/gas on flat surface or downhill, uphill doesn't seem to be quite as loud)
3.) Noise gets progressively louder with speed, but does not change with shifting of tranny
4.) No difference in noise level or relation with speed with hubs locked or unlocked, 4WD or 2WD
5.) Vibration can be felt in transfer shifter that relates to speed/gear noise (IE more vibration when louder)
6.) Fluid level and condition check okay (low when noise first started but topped up, no burnt smell or signs of metal shavings after drain and fill)
7.) Rear driveshaft does need new ujoints, there is a decent amount of play in any direction on the rear DS

I'm thinking (hoping) this could be a bad output bearing, but I also know nothing about transfer cases. Does the rear output bearing sound like a likely culprit, or could it be a gear or set of gears that are not meshing just right? Or, could new ujoints on the rear and a driveshaft rebalance solve the issue? Those should probably be done anyway, as I have no idea how old the ujoints are, and they're definitely worn out.

To that end, if the rear output bearing is a likely culprit, is this something able to be replaced in the driveway, or is this professional shop territory? I did just finish a double steering knuckle rebuild and inner axle seal replacement so I'm feeling a bit confident from having done that, but the TCase is new territory for me...

Hopefully I painted a good picture of what I have going on here. I can also take and post video if that would help. If anyone can decipher everything I just put up and has some tips, I would love to hear them...Thanks in advance!

 

[OSS]

This got long-

Since the rear DS U-joints are worn & loose, start there first. Those need to be replaced anyway. Ideally, the DS should be dynamically balanced at a driveshaft shop afterwards. The two times I've had my rear DS u-joints replaced, the old counterweights were removed & new ones of different weight & at a different location were welded back on.

Then while the DS is off, check out the transfer rear output shaft bearing if you think that might be the culprit. It's easy to remove the bearing retainer while the transfer is bolted under the truck. Buy a new gasket & oil seal before removing the retainer. Don't reuse the gasket.

But before you unbolt anything, check the preload or tightness of the output flange by turning it & wiggling it while the transfer is in neutral. Ideally there should be a little drag. No wobble. No looseness.

The output shaft rear bearing is a tapered roller bearing similar to the front wheel bearings. If the rollers rattle around a lot in their cage or look contaminated, the bearing/s should be replaced. Take a close look at the bearing race pressed into the retainer. Maybe use a magnifying glass. Look for contamination embedded in the metal. Small dark specks or lines showing metal debris that has been ground into the race.

If it looks good enough (nothing obvious) now is a good time to replace the oil seal too.
Ideally, the bearing preload should be checked with an in-lb torque meter when the BR is reinstalled & if too loose, an extra shim should be added to the retainer behind the race.

If the rear bearing is suspect, all the bearings in the case are pretty much in the same boat, as they all pretty much wear at the same rate. That would require a transfer case overhaul.

But sometimes whining gearboxes & differentials are caused by worn gears that at some time in their life were run low on oil. The contact surfaces of the poorly lubricated gear teeth wear abnormally, which creates larger, flatter contact surfaces, which creates more noise.
Gears worn like this can still outlive the vehicle if they stay lubricated, they'll just be more noisy doing it.

 

[CaptHamster]

@OSS thanks for the info. Follow up questions and info!

Ujoints are definitely first on the list to replace. I did just grease the crap out of them and the slip joint which was also needed.

I did also do another drain and fill of both the transfer and rear diff. Rear diff was fine, however on drain of the transfer, I did find a decent amount of metal flakes and shavings on the end of the magnetic drain plug. I didn't get a picture, however I'm confident saying that these weren't finely ground little bits of metal (glittery looking), these were actually metal shavings, some about half the size of my little fingernail. Obviously that's no bueno, but to me that indicates that gears are no longer meshing correctly and are shaving bits of themselves off. That sound correct?

Also I did refill the transfer with Mobil 1 synthetic which seemed to quiet it down a lot, but it's still very obviously there. I think I might have to take it in to a shop to have the transfer looked at. While I would replace the bearing, I'm no longer convinced it's just bad bearing whine. It's developed to a point that's now starting to sound like a grinding or improper meshing of gears, and the metal shavings seem to back that up.

My question then is this: What would cause such a sudden downturn of the operation of the transfer? I would say this noise really began back in February of this year after I got my other new car. Since then, I have put probably 500-750 miles (if even) on the cruiser, and it has continually gotten worse, even after checking fluid levels and two drain and fills. I don't know much about how gears are meshed in the transfer, but is it possible that something came undone or wore down to a point where the gears just aren't meshing or aligned correctly anymore and are just shaving bits of themselves off? Definitely sounds like I'll be sending it off to a shop for a closer look, but my bigger concern is how quickly this progressed in terms of miles driven.

 

[OSS]

I can relate my experience with my cruiser-

If I run the transmission (H55F) long enough between oil swaps (I always use synthetic gear oil) there's -always- some fine metal powder on the drain plug magnet. Fine powder (soaked in oil) not metal flakes. Maybe a few tiny flakes if I've been grinding into reverse. That has occurred since the day the transmission was installed 28 years ago.

When I drain the transfer, for the 30 years I've owned it, the drain plug magnet is always virtually clean. Almost zero metal dust on it. Way less than the transmission. I used Mobil synthetic in that for 28 years.
If you're seeing big flakes on the TFR plug, that's not normal and using fancy oil won't stop the mayhem.

As I see it, the point of troubleshooting is to determine whether something needs further inspection. I think it's pretty obvious that something isn't right inside the TFR case if you're getting a lot of biggish metal flakes & excessive noise.

I think that removing the rear TFR cover and having a look see would be the best thing to do. Once it's apart it will be pretty obvious what went wrong and what's grinding down.
The answer will be staring right at you. We can guess what might have happened, but when the case comes off & the parts get inspected... you'll likely have your answer.