Metal bits found in rear diff

[kcjaz]

So after I fixed my front diff/CV issues I decided to take a UOA of the read diff fluid to potentially use as a comparison to the UOA I had done on the front as the miles on the oil was the same for both diffs. I found this:

I didn’t expect that with only 7200 miles on the oil.

I regeared (Nitro 4.88s) and did lockers a little over 4 years ago. 3 years ago, I wrecked my rig and moved all my mods, including the diffs and complete rear axle to my current 200. All’s been fine until now. The only thing that makes we wonder is that after we did the swap over I would occasionally notice a gear whine or whistle when coasting at 40 to highway speeds. It would stop the second I give it gas. I could not ever tell where it was coming from though. It could be any of the gear boxes or the transmission (yes, I moved the transmission and transfer over to the new truck when we did the swap because I knew the history of those components and the transmission only had 30K on it.

So, what to do next? I’m getting ready to go to Moab in April and am planing a 2 to 3 week overlanding trip around that. I don’t really want to be in the middle of the desert and have my rear diff grenade.

My first step here is to fill the diff with new oil and put some miles on it then check the oil again and see how it looks. I’m not sure what “some” miles is. I’ve thought about just driving 5 or 6 hours out and back just to get 700-800 miles.

Or, maybe I just need to bite the bullet and pull the rear carrier assembly and take a look. I did put my borescope in the fill and drain holes and didn’t see anything except nice and clean gears and metal surfaces. It’s a very limited view but it wasn’t all nasty, far from it, it was pristine. The sludge was at the bottom on the diff. Not sure how big of a job pulling the carrier is. I would assume the axles would need to be pulled to do it. I’m sure I could figure that out but if I find a bad bearing or gear, then I’d be stuck and would have to get the truck to someone with more skill/knowledge than I have.

 

[Sandroad]

So all that occurred in just 7200 miles? The sludge and dark oil is more than I would want to see, but the metal chunks are really not good. Something is damaged or disintegrating in there and just changing the oil and hoping is not what I would do. The boroscope is only going to give you a partial view, but there is something going on if you find metal chunks like those. But, look for other opinions; I'm a long way from being expert in differentials.

Edit: Any chance that resulted from the mangled diff plug repair last year?

 

[kcjaz]

So all that occurred in just 7200 miles? The sludge and dark oil is more than I would want to see, but the metal chunks are really not good. Something is damaged or disintegrating in there and just changing the oil and hoping is not what I would do. The boroscope is only going to give you a partial view, but there is something going on if you find metal chunks like those. But, look for other opinions; I'm a long way from being expert in differentials.

Edit: Any chance that resulted from the mangled diff plug repair last year?

For sure something is wrong and has disintegrated to some extent. Before the mangled diff plug, I had a plugged breather which cause some leak at the axle seals. It wasn’t a big loss of fluid. I discovered the mangled diff plug while at Moab last year. The plug had been knocked loose and was dripping. I added a little fluid but again, it wasn’t much.

On a side note, I’ve never been able to put the FSM 4.49qt in the diff. Usually, I can only get 4 qt in. This time I drained 4.25 qt but I let it drain over night and lifted the driver rear about 8-9 inched to tilt the truck tore the drain plug. Oddly, I can now only get about 3.8 qt in so I’ve letting it sit and then will drive a little then check again.

I agree that just hoping isn’t really a plan. I’ll be talking to the shop who did my gears and see if I can get it in.

 

[kcjaz]

Here the noise I hear:

 

[linuxgod]

Here the noise I hear:

I hear it.

Diagnosing Differential Problems - West Coast Differentials

Diagnosing differential problems can be tricky. Have a grind, whine, howl, chatter or clunk? We can help you diagnose it, and we have the parts to fix it!

differentials.com

Typically the noise means the pinion depth is off, I think because it’s too tight - which sucks because there’s a crush washer...

I believe you can get noise if the pinion bearing is going bad too, which might explain the metal bits.

 

[kcjaz]

I hear it.

Diagnosing Differential Problems - West Coast Differentials

Diagnosing differential problems can be tricky. Have a grind, whine, howl, chatter or clunk? We can help you diagnose it, and we have the parts to fix it!

differentials.com

Typically the noise means the pinion depth is off, I think because it’s too tight - which sucks because there’s a crush washer...

I believe you can get noise if the pinion bearing is going bad too, which might explain the metal bits.

Differentials.com.

Well, maybe better than new gears. Not sure what crush washer your are talking about:

 

[linuxgod]

Differentials.com.

Well, maybe better than new gears. Not sure what crush washer your are talking about:
View attachment 4099822

41231, maybe? I’m definitely not an expert though

 

[ElJayBird]

Isn't gear whine a common complaint with Nitro? I'd been considering dropping them into my truck as well but a local shop talked me out of it because they see them come back so often with customers complaining about the whine.

 

[bloc]

Differentials.com.

Well, maybe better than new gears. Not sure what crush washer your are talking about:
View attachment 4099822

Probably meant the crush sleeve, PN 41231. Once it’s compressed it can’t be reused.. or even, a really hard hit of the pinion driveshaft flange onto something can compress it and throw preload and pinion depth out of whack.

That’s why some people run a solid spacer that needs to be shimmed instead.

Do you feel any grittiness turning the pinion flange with the driveshaft disconnected? Preferably with tires/wheels off as well.

 

[kcjaz]

Probably meant the crush sleeve, PN 41231. Once it’s compressed it can’t be reused.. or even, a really hard hit of the pinion driveshaft flange onto something can compress it and throw preload and pinion depth out of whack.

That’s why some people run a solid spacer that needs to be shimmed instead.

Do you feel any grittiness turning the pinion flange with the driveshaft disconnected? Preferably with tires/wheels off as well.

I just rotated the tires and readjusted my park brake so I had it in the air and all four wheels off I could’ve easily checked that but she’s buttoned up and on the ground now and I need to head back to KC. I’m gonna take it there where I’ve got more resources to figure this out and get it fixed.

 

[kcjaz]

I’ll be able to have the shop that did the regear take a look next week. I am hoping that it is “just” a bad pinion bearing, and if so that its the front one because that can be replaced w/o total disassembly (at least the FSM shows that). You can remove the parts all the way to the spacer that’s in front of the rear bearing. If the rear bearing is bad, it looks like the whole carrier needs to be disassembled. If it is the rear bearing, the next issue is that bearing is backordered with none in the US…. I think I’m just going to order the parts and get the backorder going. If I get lucky, I can just cancel the rear bearing.

 

[linuxgod]

Was it Toyota bearings used in the regear or Nitro?

 

[kcjaz]

Was it Toyota bearings used in the regear or Nitro?

Great question. Not sure but I think Toyota but I’ll find out as the guy who did the regear will be the one looking at it now. Toyota US doesn’t seem to have any of the rear bearings but PartsSouq does so I ordered there.

 

[linuxgod]

Great question. Not sure but I think Toyota but I’ll find out as the guy who did the regear will be the one looking at it now. Toyota US doesn’t seem to have any of the rear bearings but PartsSouq does so I ordered there.

I’m hoping it’s the pinion bearing for you. Easiest to access though TBH given the metal bits I would be inclined to still pull the 3rd and inspect and clean everything thoroughly.

FWIW when my gears were done the shop was unimpressed by the fitment of the nitro bearings. And the rear pinion seal leaked. If I was ever doing gears again in would throw out the kit bearings and seals and not use OEM.

 

[kcjaz]

Update: Got into the shop. the pinon was pretty loose. We pulled the pinion seal and but could really see anything and didn't have a way to pull the front bearing. W/o Toyota's SST I don't think you can pull the bearing the FSM way. Even after watching a video of someone using the SST, looking at it in person, I don't see how/understand how the SST actually grabs the inner race. Anyway, all we did was tighten the preload on the bearing by “feel”. I don’t really have this “feel” though now, I know what it felt like before and how it now feels so maybe I could repeat this (no likely, who am I kidding). We also scoped the diff from the fill plug and didn’t really conclude much other than we didn’t see any significant carnage. Couldn’t see the rear bearing where the damage is likely to have occured.

What we did is not the right way to fix this but the shop can’t get me in to from the 3rd and replace the bearings. During a post tightening test drive, the hear while when decelerating was almost gone. Just barely there and you really had to focus on listening for it. I took it on about a 40 minute freeway drive and when I got home, I took my IR gun to see if the diff was abnormally hot. The problem here is I don’t really know what normal is. I measure where the pinion bearing are and got ~143F.

For reference, I measured the front diff and got about the same. 143F doesn’t seem crazy. The rest of the diff was around 120F. My plan is to put a couple hundred miles on it and keep monitoring temps and how the drive shaft flange feels. I’ll also pull the drain plug and see if I find more metal fragments. If things don’t seem to be getting worse, then I think I’ll take the chance and roll to Cruise Moab and just keep keeping an eye on things during the trip. Then fix this when I get back (hopefully under my own power).

 

[GrouchyTech]

You need to be accurate on your preload. Humans are very very bad at gaging weight/force, especially with something as low as that bearing preload.

You really need to pull that third member out and inspect everything closely.

If it starts making noise again, it’s probably going to develop quickly.

 

[GrouchyTech]

Also, **** that SST. Some of them are great. That one isn’t.

 

[kcjaz]

You need to be accurate on your preload. Humans are very very bad at gaging weight/force, especially with something as low as that bearing preload.

You really need to pull that third member out and inspect everything closely.

If it starts making noise again, it’s probably going to develop quickly.

Agree. I don’t like “feel” either and love my torque wrenches. I use a torque on my oil filter. However, Trying to measure a preload of 9 - 12 in-lb in this situation isn’t really possible as there are too many other things causing friction. Doing this is a stop gap measure. You are trying to tighten the nut to “325 ft-lb or less” to get that super low preload. Even doing this on a bench would be challenging.

Something is no good inside for sure. The nut was still staked in the install position. I think that means that the rear bearing had to move or something happened to the crush sleeve but I don’t understand how either of those things could be. We tightened the nut almost a full turn from where it was originally staked.

I agree that if the noise comes back it will do so soon. If that happens, I’ll have to come up with a plan B for Cruise Moab.

 

[kcjaz]

Also, **** that SST. Some of them are great. That one isn’t.

Interesting. Looks slick in this video:


I almost bought this but when we fix this the right way, we will be able to use the press. What sucks about it?

 

[bloc]

How did you decide how much to tighten the pinion nut? When you say "feel".. you mean pinion preload feel? How much torque did it take to tighten the nut? (ie, did it seem like you were still crushing the sleeve?)