My rear... is groaning

2003 TRD Offroad
Extended cab
V6 Auto 4x4 with E lock

So here's my story. A little over a year ago I noticed that my rear was getting a buildup of oil. Popped my head below the bumper and noticed that there was oil leaking from my differential. Not the fill plug... not the drain plug.... but my actual differential - oil was leaking through the steel axle. Did some research and determined that with about 185k miles, JB Weld was going to be my remedy. Made the patch and filled her up (if I remember correctly it took about 1.5 pints to bring it back up to the proper level.

Long story shorter...

Since that time, my truck has had a groan/rumble/hum between 50 and 55 mph and regardless of accel, decel, throttle position. Always thought that it was a result of running with low oil until I noticed it. Since then I have also have had a steering rack replacement (rusted right through the body of the rack beneath on of the mounts). Anyway, apparently the oil on my tailgate from the steering masked oil from the differential. Over the past week or so, the rumble/groan hum began to occur at lower speeds, and most particularly when decelerating. On the way home friday the fairly benign noise became much more... aggressive, for lack of a better word.

The groan/rumble/hum became a growl/grindy kind of noise. Opened up the rear diff fill hole and found I was waaay low on oil. Ended up dumping about 4 pints in to bring it to fill. Drove it, and the real loud noises are gone, but now it occurs at all speeds, but is related to throttle. If I come off it, there's a hum. If I then apply very very light throttle, I get a whine. Full throttle no noise.

From reading I think it's pinion bearing(s), but looking for potential others causes.

Anyone have a link for "checking" or replacing pinion bearings (with pictures)?

TIA!

 

It is definitely time to take out your rear and have someone take a look at it. (mechanical Proctologist). Fix the hole, corrosion resistant coating applied, gears checked and tolerances checked.

 

I should add:

1. 204k miles
2. After filling to test it had to drain is somewhat to patch the hole. Upon draining a little I noticed some metal, so I drained it completely and refilled. The magnet had a thin layer of metallic sludge (very fine) and a few flakes.

 

Anybody know of a good gear shop in Danbury, CT?

 

....also, what happens when a differential fails? Rearend lockup? I do a lot of highway driving; that scenario could be problematic at highway speeds.

 

Lockup is unlikely. Bearings will wear, cause excess backlash/slop, chowder up the gears, eventually blow. When that happens you slam her in 4x4 and go on with your day

^^^id fix before that happens ahaha.