Can Anyone Diagnose this Sound coming from my Differential ?

[brightstar]

Wifey wanted to move our QX4 for me , and was in a hurry, it was parked pointing downhill, I should also say it has 336,000 miles on it. And the transmission is a little lazy to actually engage once you select a gear, just a second or second and a half, but just long enough so that if you select a gear and don't wait for it , your RPM's can climb to about 1300-1600 before it engages........ All original running gear , well till now
she jumped in
Started it up and put it in reverse , hit the gas and BANG !! clunk !! and no movement ,
So , I jacked up the back axle, plus jackstands, and front tires blocked, started it up , put it in reverse and released the parking brake , grind/ clunk, put it back in neutral, w/o parking brake, the rear tires should freewheel , Nope ! driver side is locked , passenger side moves barely with a LOT of force.
I'm guessing the spider gars in the rear differential are toast or the pinion carrier. FYI: It is a Limited Slip/ posi unit as well.
Here is a youtube video I made of it , I'm in reverse to begin with then I shift to forward , It has this dadadadada noise and only one tire moves, i'm thinking the spider gears are toast .

https://www.youtube.com/watch?v=w6Q_W1Lv13A




Can anyone confirm ??
thank you in advance

[mdmellott]

There is no way to specifically diagnose that without dismantling the differential. I can definitely say that it is broke beyond any basic repair and would likely cost less to simply replace the differential than to have it repaired. There are so many moving parts in there, broken bits of gears will have damaged other parts when it failed.

I would be curious to see what falls out if you remove the drain plug. Differentials will eventually fail catastrophically if the gear oil is not periodically changed and if the gear oil has leaked out to the point where there is no longer adequate lubrication. It is too often an overlooked maintenance item.

[Hawairish]

I've rebuilt a lot of these units, and I can't say I'm convinced it's the side or spider gears. Since the passenger tire still spins independently of the drivers side, those gears must be working properly to some degree. If they were bound up, both tires would spin together as if it were locked. Even with a chunked tooth on a spider gear on a 4-pinion setup, the other 3 would pick up the slack. Noise and binding issues would be more present in a 2-pinion setup, which this LSD is not.

My thought is the driver's side wheel bearings have failed. This could potentially seize the axle shaft, explaining why only the passenger side rotates (the engine has ample power to overcome the LSD's break-away torque). Rotating the passenger tire by hand (even with parking brake off and truck in neutral), you would expect both tires to rotate together because of the LSD, but if the driver's side wheel bearings were seized, you'd essentially be trying to exceed the break-away torque of the LSD by hand, which should be difficult (particularly for a 2001 which had higher break-away specs).

What you can do is detach the driver's brake hydraulic brake line from the wheel cylinder, detach the parking brake cable from the trailing arm to get some slack, remove the brake drum, and then undo the four (4) 17mm nuts at the end of the axle tube. (You do not need to drain the diff, provided you don't let the axle tip downward to spill out the axle end.) This will allow you to slide the axle shaft assembly out of the axle housing a little (may need a dead blow hammer or mallet, or slide puller on the wheel studs), enough to clear the studs from the axle end. This will pull the axle shaft end out of the differential as well. You should be able to easily rotate the axle shaft relative to the brake backing plate and all the attachments. If the axle shaft doesn't rotate freely, it's the bearings.

Notably, any defect with the brakes that would cause the driver's side tire to lock would have the same effect, so inspect the brakes. I don't think this is the cause because nothing brake-wise would produce a bang, but inspecting them is along the way.

At that point, with the driver's axle shaft pulled out a little, you can also try rotating the passenger axle shaft with the truck in neutral. It should rotate easily. You can try rotating that tire with the truck in park, but you'll still need extra effort to overcome the LSD (easier done with tire still attached). If it can budge a little, then the side and spiders are likely fine.

[Hawairish]

Also, in the video, I do see the driver's tire twitch when accelerating and letting off, which could just mean it's not seized, but is binding. These sort of wheel bearings tend to use plastic cages on the rollers, and more so than a metal cage, once compromised, it's easier for a roller to get misaligned.

[mdmellott]

I've rebuilt a lot of these units, and I can't say I'm convinced it's the side or spider gears. .....

Excellent descriptions! You know this well. Just read through your write-up on NPORA posted last year on how to repack a H233B LSD.

[Hawairish]

Excellent descriptions! You know this well. Just read through your write-up on NPORA posted last year on how to repack a H233B LSD.

Thanks! Yeah, I've really taken to the H233B over the years. LOTS of LSD rebuilds/repacks, locker installs, axle and diff rebuilds, gear swaps, disc brake swaps, misc. projects, yada yada. I have a "spare" axle in the garage, and I even swapped one into my 98 2wd Frontier not too long ago. Coincidentally, that truck busted some spider gear teeth many years ago in its original H190 axle, so I know firsthand how a 2-pinion open diff might behave under the those conditions, too. Funny thing is that the truck was still fully drivable, it'd just clunk every now and then around a corner if it didn't mesh just right.

Notably, if it is a bad wheel bearing, it's a bit more complicated and expensive to repair than just swapping out the 3rd member on the housing. Part of me hopes it's something in the diff because a used diff is pretty easy to source and swap ($450 is pretty high in my neck of the woods), vs. tearing down an axle shaft. Fortunately, if the bearing is bad, you're just a few more steps away from pulling the axle shaft assembly off the truck and taking it to a shop for repair. Just need to pull the brake shoes and detach the parking brake cable. Changing the bearings is not something that can be done at home without access to some specialty tools, unfortunately.

Also, if pics help, this is the essence of what we're trying to do here:



With the axle shaft assembly out like this, the axle shaft should be able to rotate in the bearing cup attached to the brake backing plate.

[Hawairish]

I found myself watching the video a few more times and there's still something I can't wrap my ears around.

At the 15s mark, there's a brief grinding sound, then a longer grind at 16s before the passenger wheel starts spinning. The driver wheel does a twitch as if it is trying to go into reverse right before it binds and the passenger wheel starts. The rumble sound at 17s and later at 33s is likely the meshing of the side and spider gears (with driver side gear remaining stationary and 100% output through the passenger side gear), but I'm surprised to not hear the same grind around the 30s mark. Notably, the audio seems to pick up noises really well so it's hard to know where it's coming from on the driveline. Since I see the load sensing valve spring and lever adjusting when gas is applied, the noise could just be something else binding up along the driveline (at first it sounded like a transmission sound trying to engage reverse).

But, the grind is of interest. It's such a quick/fine sound that it gets me thinking about the axle shaft splines or the LSD friction plates, which have fine grooves in them. Spline failure is unlikely, since the sound would be repeatable. Friction plate failure (like a cracked piece) is possible, but would be pretty mundane and if it locked up the side gear, it would cause shaft to spin. So, again, seems like the driver's side gear is stationary while the diff is spinning, and the only place it could seize would be at the wheel bearing.

[brightstar]

I have been trying to get the drain plug out for almost 8 hours now , it not budge, I tried my 1/2" bar on it 12" long , then attached another 2 foot bar on that for about 3 ft of leverage, then I pulled out the big gun, my Makita Impact driver, the XWT08 , that is suppose to over 700 ft/lbs of torque. AND NO GO !!
I'm soaking it with PB Blaster right now , and banging on it with a 2lb ford wrench, (mini-sledge).
Hopefully sometime before Halloween I can bust it loose.
Some of the noises in the video are me applying and un-applying the brakes, and shifting from forward to reverse. I will make another video wife the wife in the driver seat and me moving the camera around and narrating what is going on, also moving in closer to better isolate where the exact sounds come from.

Thank You Guys !! stick around more to come !!

[Hawairish]

The last R50 I worked put up a fight, too. Busted my drive adapter. Try some heat, and also try to tighten it a little first, then loosen. Also, remove the fill plug first if you haven't already, just to make sure you've got the means to fill it.

Keep in mind you can do my steps above to pull the axle shaft without draining the diff. Just keep the driver's side of the axle tipped up a little.

[mdmellott]

The first time I tried to remove my drain plug, it would not budge with my 1/2" square drive 18" breaker bar and I almost wrecked it as the square plug hole started to round out. The plug is actually a 13mm square and the 1/2" drive being slightly undersize with rounded corners was just about to cause me a nightmare. I bought a 13mm square adapter, which has much smaller radiused corners, and applied heat with a propane torch to area around the plug. It finally started to turn. Never had that issue again on later removals after reinstalling it with Teflon anti-seize lubricant.

[Hawairish]

Yep, it’s a 13mm square socket…practically a must-have for this effort. I have one, too, but it’s 3/8” drive so that’s where my 3/8”-1/2” adapter gave up the ghost on my 30” breaker bar. A lot of words were exchanged that day.

I also only ever use Teflon tape.

[Hawairish]

Thank You Guys !! stick around more to come !!

Any luck?