Whine during acceleration & deceleration - load related

[masospaghetti]

I have an opportunity to pick up a 1998 XLT 5-speed, 4-door, 4WD that I owned about six years ago. I gave it to my brother who no longer needs it, so I am trying to get it home. Vehicle is in CA and I'm planning on driving back to NC. Just over 250k miles.

Here's my question. I drove it today for the first time in a long time. There was a noticeable gear whine that was load dependent - Accelerating or decelerating heavily in 1st gear made the noise the most pronounced. I could hear it in 2nd gear but less noticeable. No noise in neutral or while coasting in gear.

Bad pinion bearing in one of the differentials? Could it be transmission related? Trying to prevent a breakdown somewhere in the middle of nowhere.

 

[imp]

@masospaghetti
Whine, or like "singing", ring & pinion, cause either scored teeth, or misalignment due to differential bearings. Very high pitch more like grinding sound, pinion bearings. Can you discerne whether front or rear? Likely rear since related to load; this is not an AWD?

Given the plan to drive it 3000 miles, I would put it up on sturdy stands, have a friend run it in 4th. or 5th. gear, set in 4X4 HIGH, while you listen via a stethoscope at the differential center sections, under the pinion bearing, and the wheel hubs, all 4. I had similar noise I almost could have sworn was differential originated, steth. proved wheel hub bearing.

The steth. can be a long screwdriver, the blade end placed against the various housings, the rounded handle pressed against your ear. Or, a length of rubber vacuum hose.

Some have derided me for this offering. Too dangerous. Ya gotta be careful, have the best support stands possible, not piss-poor Chinese junk, that you've used OK in the past. Good luck. imp

 

[masospaghetti]

Thanks imp. Sounds like "singing" to me coming from the front half of the vehicle but it's hard to tell. It's a 4wd not awd so there wouldn't be any load on the front differential, right?

 

[imp]

Thanks imp. Sounds like "singing" to me coming from the front half of the vehicle but it's hard to tell. It's a 4wd not awd so there wouldn't be any load on the front differential, right?

@masospaghetti
Correct, there would be little load on the front differential running in 2WD. However, damaged ring & pinion gear teeth can and will "sing" even without load. Assuming it originates up front, other noise-producers include wheel bearings. C-V joints generally won't make a humming sound when bad. Most certain way to pinpoint is with a stethoscope. For example, I once was certain the noise was due to gear teeth, having heard such dozens of times in the past. Under the vehicle with my long screwdriver handle pressed to my ear, the sound could be heard around the differential area, but was surely loudest out at the left wheel spindle. Here's the wheel bearing, torn apart:

The outer race of one bearing had galled to the extent that the rollers "sang" their way over the rough spot. The noise was only slighly noticeable at first, and the condition shown took several thousand miles to develop. Reason was the roughness began in the center of the raceway, allowing the rollers to still run over "good" surface. Saved tearing into a differential having no problems. imp

 

[masospaghetti]

Wheel bearings can make "load-dependent" noise? I've had a few bearings go bad before but the noise they made only depended on speed. I assume a bad/failing transmission or transfer case bearing would make a similar noise?

Other than this noise (which is really only noticeable in first gear) it's amazing how well the truck still drives, even after sitting for six months with a dead battery and stale gas.