Gear Noise from Transfer...Bearing?

[trinhtiet]

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!

 

[FJ60Seth]

If you suspect rear u-joints you could test by removing the rear drive shaft and driving normally in 4WD high. I drove like that for several hundreds miles after I broke my rear drive shaft, with no issue. Others have done the same.

 

[3_puppies]

what series rig? stock running gear or are there changes?
any play in the diff input?

 

[OSS]

Bearing growl (due to worn bearings) and gear whine (due to excessively worn gear teeth contact surfaces) are two very different sounds. One growls & rumbles, the other whines.

If a gearbox (transmission, transfer case or axle differential) is run too long or too hard with insufficient oil, stuff will wear quickly. Gear teeth normally contact each other on small contact patches but if they're run too long with insufficient oil, that contact patch will wear and get bigger & flatter and the gear will make more noise & whine. There can still be tons of life left in the gear, but it will never be as quiet as it was when new.

The $20,000 question is.... how long did the transfer run low on oil...

 

[DevonBen60]

This sounds like the transfer box idler shaft is getting worn by the pair of bearings. Did it start in 5th gear then 4th? The above is consistent with noise only under load. Once wear starts there is no stopping it

 

[Dynosoar]

1. Check the oil level
2. when the shifter bushings go bad the shifter begins to transmit a lot of weird noises that were hidden before. Gear drive cases will always make some noise.

Dyno

 

[CaptHamster]

What the heck? Not sure why, but this post is a word for word copy of a post I made a few months ago...

Gear Noise from Transfer...Bearing?

I knew I wasn't a terrible writer but I didn't think I was worthy of plagiarism just yet

Well regardless, allow me to add my experience and (almost) resolution to this issue.

Tore down the case and discovered the idler shaft surface was ruined, which unfortunately also damaged the inner surface of the idler gear. Thanks to @orangefj45 I was able to get a rebuild kit and replacement gears and am in the process of rebuilding the transfer. Glad I got to it when I did, as the idler shaft was losing lots of material that was floating around the transfer. Saved myself some headache in the long run, and it's definitely obvious why it was making that awful noise.

I also say that this issue is (almost) resolved, because until I put everything back together, I can't be sure that the idler shaft and gear were causing most of the noise and vibration, though it doesn't look like anything else was out of whack enough to cause problems. Ujoints seemed okay, they're getting replaced anyway but none were obviously damaged or having issues.

 

[orangefj45]

It's pretty simple to diagnose where the noise is coming from ..... I'd run the vehicle on jack stands and use a stethoscope. It'll allow you to pinpoint the culprit.
I'd suspect either an idler shaft bearing or the rear output. Since the case was rebuilt 5 years ago, I'd suspect the rear output since the idlers are usually good for 150-200k miles. There was a short run of kits on the market with improperly hardened idler shafts. I've seen a couple of these. One failed with less than 15k miles on it.
The rear output bearing is easy to diagnose; if you can grab the rear output flange and move it up and down ( even very little ), then there isn't sufficient bearing preload. This can be caused by a spun race in the rear extension housing.
Hope that helps.
Georg @ Valley Hybrids & Cruiser Brothers
Shop 209-475-8808

 

[DevonBen60]

[/QUOTE]

It's pretty simple to diagnose where the noise is coming from ..... I'd run the vehicle on jack stands and use a stethoscope. It'll allow you to pinpoint the culprit.
I'd suspect either an idler shaft bearing or the rear output. Since the case was rebuilt 5 years ago, I'd suspect the rear output since the idlers are usually good for 150-200k miles. There was a short run of kits on the market with improperly hardened idler shafts. I've seen a couple of these. One failed with less than 15k miles on it.
The rear output bearing is easy to diagnose; if you can grab the rear output flange and move it up and down ( even very little ), then there isn't sufficient bearing preload. This can be caused by a spun race in the rear extension housing.
Hope that helps.
Georg @ Valley Hybrids & Cruiser Brothers
Shop 209-475-8808

My replacement idler shaft was a non original and lasted just 2k before i could hear a problem.
Changed it for an original sourced in Germany and it has been fine ever dince