Metal bits found in rear diff

[kcjaz]

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?)

Not very scientifically. The guy doing the work has built a lot of diff and is a mechanical engineer that now operate a cruise shop. I’m definitely more anal retentive than he is with procedure and torque specs. Causes some discussions and eye rolls both ways.

Anyway, to answer your question, we just incrementally hit it with an impact then rotated the flange back and forth until he was happy. We did not pull the rear tires, or put the truck in neutral, which may have been what we should have done but when I’ve done essentially that in the past to just rotate the drive shaft, it takes a lot more than 12 in-lb to rotate the drive shaft flange. I think you’d have to pull the axles to have a shot. I’m fairly certain, if we had tries to get a measured 12 in-lb, we would have still had slope and noise. Could we have over tightened it? Yes, though the tell tail whine while decelerating, of a loose/bad pinion bearing is way better but still slightly there. I’m hoping this means we didn’t over tighten it and the diff is serviceable enough to make the Moab trip. But, the reality is that there is no way to know this other than pull the 3rd and doing this the right way.

 

[bloc]

Not very scientifically. The guy doing the work has built a lot of diff and is a mechanical engineer that now operate a cruise shop. I’m definitely more anal retentive than he is with procedure and torque specs. Causes some discussions and eye rolls both ways.

Anyway, to answer your question, we just incrementally hit it with an impact then rotated the flange back and forth until he was happy. We did not pull the rear tires, or put the truck in neutral, which may have been what we should have done but when I’ve done essentially that in the past to just rotate the drive shaft, it takes a lot more than 12 in-lb to rotate the drive shaft flange. I think you’d have to pull the axles to have a shot. I’m fairly certain, if we had tries to get a measured 12 in-lb, we would have still had slope and noise. Could we have over tightened it? Yes, though the tell tail whine while decelerating, of a loose/bad pinion bearing is way better but still slightly there. I’m hoping this means we didn’t over tighten it and the diff is serviceable enough to make the Moab trip. But, the reality is that there is no way to know this other than pull the 3rd and doing this the right way.

So assuming he could match the preload spec by hand, which I understand is basically impossible, but as a hypothetical.. the reason he'd have to tighten the nut a full turn to match the original preload is a full thread's worth of material has been taken off the bearing faces and/or rollers. Technically when you consider stretch and how much the metal itself "moves" during tightening that comes out of that full thread distance.. but hopefully you get the idea. Or at least that's the logical path to one additional turn.

Most likely the reason the noises have subsided is the pinion isn't moving around anymore on accel/decel. Whatever the pattern is now, it's not changing.

Now as you say if he likely went past 12in-lbf of preload.. who knows. But at the end of the day the reason the nut had to turn is some material has come off the bearings. They probably won't go very long like that. Personally, I'd be very nervous taking a roadtrip in that condition.

Another hypothetical.. assuming the bearings would survive this long-term, that means the pinion moved away from the ring gear by however much the large bearing has been impacted. You'd likely have wear on both bearings so it's really difficult to try and guess this number, but also end of day it will impact the tooth engagement.

 

[linuxgod]

I’m with @bloc, driving that far on a bad bearing would make me nervous. Do you trust the local dealer or another shop or is there a gear and tranny shop near you? It shouldn’t be more than a day to pull the 3rd and replace the bearings. It certainly could be worse when you get it opened up but I’d like to think the bearing is it. The danger of running too far with a bad pattern is that you end up damaging the gear set, and I’ve heard Nitro 4.88’s aren’t available anymore for our diffs so if that happens it’s a much harder road to repair.

 

[GrouchyTech]

I’m with @bloc, driving that far on a bad bearing would make me nervous. Do you trust the local dealer or another shop or is there a gear and tranny shop near you? It shouldn’t be more than a day to pull the 3rd and replace the bearings. It certainly could be worse when you get it opened up but I’d like to think the bearing is it. The danger of running too far with a bad pattern is that you end up damaging the gear set, and I’ve heard Nitro 4.88’s aren’t available anymore for our diffs so if that happens it’s a much harder road to repair.

I would find a specialty shop and avoid the dealer. Almost none of us can properly setup an R&P, usually we will just replace the whole chunk. Find someone who does gear setup on a regular basis.

 

[kcjaz]

I’m with @bloc, driving that far on a bad bearing would make me nervous. Do you trust the local dealer or another shop or is there a gear and tranny shop near you? It shouldn’t be more than a day to pull the 3rd and replace the bearings. It certainly could be worse when you get it opened up but I’d like to think the bearing is it. The danger of running too far with a bad pattern is that you end up damaging the gear set, and I’ve heard Nitro 4.88’s aren’t available anymore for our diffs so if that happens it’s a much harder road to repair.

I don’t think I want any of the local dealers to touch this. I only know if two local shops that built Diffs and the specifically do Land Cruiser/Toyota. I’m using one of them now he’s who looked at my diff yesterday. Those two are the guys I trust neither has availability in the timeframe. I really need. Guess there’s no harm in asking them. Who else could do this

FWIW, I just pulled the drain plug out to look at the magnet. Only 300 miles since I replaced all the fluid and the little eye drain, drained out was pretty clean no metal fragments barely a little black sludge on the magnet.

 

[Rednexus]

I had this happen on a 8.2" diff with 4.56 gears that ECGS built for my GX470. Within about 5,000 miles it developed a noticeable gear whine upon coasting, by 10,000 miles it had developed a loud whine on coasting and a noticeable whine under part-throttle cruising. The fluid had a lot of metal when I first changed it at 500 miles, and quite a bit more at 5,000 when I changed it again (due to it making noise). The photos below show the condition of the fluid and gears at 10K when I finally pulled the 3rd member out. My OEM gearset with over 190K on it had far less wear.

ECGS rebuilt my diff for free and the new diff is fairly quiet, but does have a very light whine on deceleration. Personally - I'd pull your 3rd member and send it out-of-state to a Toyota specialist. There aren't enough folks in the Midwest who work on Toyota diffs. The local diff shop over here in eastern Missouri - reportedly one of the best in the state - declined to even attempt my diffs and thought a GX470 was a sports car. ECGS turned mine around in about a week (although, being a warranty repair on a diff they built helped). I was certainly not happy to have the first one fail so quickly, but they did go out of their way to make it right.

 

[ga12r1]

Best and easiest thing to would be send it to ECGS if you have a locker, if you dont have a locker they can build you a diff and send it to you then you send in the core once installed. I doubt ECG would want to reuse your R&P anyway (ask me how I know ) and even if you talked them into it I doubt they would warranty it.

 

[kcjaz]

Ok, I found a local gear shop that seems pretty capable and has been around a while. Plan is to take the truck to them Monday. Hopefully it’s just the bearings in the gears are in decent shape if so, I may be able to be in and out on the same day.

Assuming it’s just the bearings, they will still need to set the preload on the ring bearings, check the backlash, and do a contact pattern check just like they would if they were installing new gears , right? Will the gears need to be broken again?

 

[kcjaz]

Good “differential 101” video:



Watching the video and then reading the FSM, my conclusion is that there is a lot of experience needed to set up gears (quite the epiphany I know). The FSM is misleading or doesn’t provide total context all the time. For example, it tells you how to replace the pinion seal, front bearing, and crush sleeve and check the bearing preload with the 3rd still in the axle housing, yet the preload values it provides is only for the pinion bearings. The problem is you’ve got preload associated with the ring gear bearings and the weight of the wheels and axles. If you dig deep in the FSM it provides higher pinion preload values to check after you install the shims for the ring gear bearings. If you really did this with the 3rd mounted to the housing on the truck, you would have to pull the axles and use the higher preload numbers (11 to 17 in-lb vs, 8-12 in-lb).

 

[Rednexus]

Ok, I found a local gear shop that seems pretty capable and has been around a while. Plan is to take the truck to them Monday. Hopefully it’s just the bearings in the gears are in decent shape if so, I may be able to be in and out on the same day.

Assuming it’s just the bearings, they will still need to set the preload on the ring bearings, check the backlash, and do a contact pattern check just like they would if they were installing new gears , right? Will the gears need to be broken again?

That's a lot of metal that went though your gears and bearings. IMO even if everything looks/feels OK and they put it back together, there is low probability that your diff will last as long as one with new gears/bearings. After all, it had tens/hundreds of thousands of tiny abrasive particles floating in the fluid, along with those bigger chunks. That indicates a lot of metal has been lost, so tolerances are wider somewhere, and smooth surfaces are now worn.

I can't speak for your gears specifically or what the shop may find or conclude, but I was pretty happy that ECGS put all new bearings and gears in mine, as it's one less thing I have to worry about. ECGS is supposedly the "best" (or at least the highest volume shop) when it comes to Toyota diffs and they still managed to mess one up for me....so IMO it seems easy for even the pros to improperly set up gears.

 

[ga12r1]

That's a lot of metal that went though your gears and bearings. IMO even if everything looks/feels OK and they put it back together, there is low probability that your diff will last as long as one with new gears/bearings. After all, it had tens/hundreds of thousands of tiny abrasive particles floating in the fluid, along with those bigger chunks. That indicates a lot of metal has been lost, so tolerances are wider somewhere, and smooth surfaces are now worn.

I can't speak for your gears specifically or what the shop may find or conclude, but I was pretty happy that ECGS put all new bearings and gears in mine, as it's one less thing I have to worry about. ECGS is supposedly the "best" at Toyota diffs and they still managed to mess one up for me....so IMO it seems easy to improperly set up gears.

And I will add that ECGS warranty is phenomenal.

 

[Rednexus]

And I will add that ECGS warranty is phenomenal.

Agreed! They mailed me a diff box, paid shipping for my 3rd member both ways, and had the new one back to me in about a week, no questions asked. It's very nice to have a company stand behind their products - that's pretty infrequent these days (I had expected them to push back a little bit).

 

[Artie]

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.
View attachment 4108848

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).

I don’t have much to add to this conversation other than some experience with your temperature reading.

I recently went to Toyota 3.9 gears and during the break in I was checking the diff temps after the break in drives and some after. My temps ranged from 135°-141°. I do not believe yours at 143° to be out of the ordinary.

 

[linuxgod]

I’m not a expert but I don’t think you need to re-setup the gears, just change the bearing(s) and install a new crush sleeve and then put it back together and correctly tighten preload.

I do worry about other damage but given your relatively short time winds between now and CM I think if the gears look ok when the 3rd comes out I’d just swap bearings, make sure all the metal bits are out, then put it back together and run it for a week or two and then change the fluid again before you leave and if the fluid doesn’t have any metal bits in it I’d run it to Moab and back

Then again you’re talking to a guy that once in college drove 30 miles home without any brakes

 

[bloc]

I’m not a expert but I don’t think you need to re-setup the gears, just change the bearing(s) and install a new crush sleeve and then put it back together and correctly tighten preload.

I do worry about other damage but given your relatively short time winds between now and CM I think if the gears look ok when the 3rd comes out I’d just swap bearings, make sure all the metal bits are out, then put it back together and run it for a week or two and then change the fluid again before you leave and if the fluid doesn’t have any metal bits in it I’d run it to Moab and back

Then again you’re talking to a guy that once in college drove 30 miles home without any brakes

Some small setup might be needed.. if the new large pinion bearing isn't exactly the same dimensions as the old one the pinion depth can be off.

 

[kcjaz]

So the good news is I got into a local gear shop that was able to replace the pinion bearings and confirmed that the rear bearing was bad and the rest of the diff was ok.

Bad news is that I still hear a whine when decelerating and when I got home and took temps with my IT gun they were in the 170F range compared to 140F before. Also the used 85W/140 gear oil which I will change tomorrow.

Another curious thing of note is the shop blamed the bearing failure on running synthetic oil. Not sure I’m buying that.

 

[linuxgod]

I've heard synthetic oils don't dissipate heat as well in modified gears though I have basis to believe that's true. I do think Nitro recommended conventional oil, and they definitely recommend a heavier viscosity.

If the bearing was loose and the gear pattern was off long enough it's possible the gears are no longer aligned perfectly. IIRC a whine on decel can be fixed by making the preload ever so slightly tighter, while a whine on (light) accel requires less preload and thus replacing the crush washer?

 

[kcjaz]

I've heard synthetic oils don't dissipate heat as well in modified gears though I have basis to believe that's true. I do think Nitro recommended conventional oil, and they definitely recommend a heavier viscosity.

If the bearing was loose and the gear pattern was off long enough it's possible the gears are no longer aligned perfectly. IIRC a whine on decel can be fixed by making the preload ever so slightly tighter, while a whine on (light) accel requires less preload and thus replacing the crush washer?

What weight gear oil are you running? Don’t you have Nitro 4.88s too?

 

[linuxgod]

What weight gear oil are you running? Don’t you have Nitro 4.88s too?

I do. I started with 75w-90 but when I drained at 50k and had some sludge on the drain plug I stepped up to 75w-110

 

[kcjaz]

I do. I started with 75w-90 but when I drained at 50k and had some sludge on the drain plug I stepped up to 75w-110

Non-synthetic right? Same oil in the front?

I’m curious to know if the diff temp increase I see (~143F on 75w-90 and 173F on 85w-140) is all due to the the difference in viscosity. I was going to drain the 85w-140 today and replace with my 75w-90, as I have 4qts of Mobil 1 syn, to find out but maybe I should switch to a heavier oil. I think 85w-140 is too heavy but only because the manual says 75w-85 and I haven’t seen in any of the gear oil threads anyone running 85w-140.