Odd metal pieces on front diff drain magnet...

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I think I have a problem. Was in the middle of a knuckle job on an HDJ-81 with 180k. When I drained the diff I discovered some odd shavings on the magnet. I'm used to seeing a few fine shavings from gear wear but this had many small shiny thin flakes, including a thin rounded bit of what looks like a delaminated bearing surface. Anyone seen this before. Pretty sure I need to pull the third member and have a look. This could explain some odd noise and vibrations I was getting at moderate highway speeds....
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IMG_0483.JPG


I should note I had recently replaced fluid with Amsoil Full Synthetice 75W-90 about 2000 kms ago. No sign of odd shavings at that time. Seals leaking at both diffs and front of transfer case since i switched to the Amsoil as well (may be separate issue)
 
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LINUS

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IDK what that near-washer piece is, but I bent the shell & the inner PS driveshaft wore the splines into the spider gear & eventually or right away my spider gear portion cracked into big chunks but I drove on it for ~500mi before I bought a whole brand new e-lock diff that someone traded into Slee (mini-truckers like them for RR diffs, so I was told)

It took a while for me to realize I bent the shell, but then when I measured I was about 1/2” off from a hard drop my passenger didn’t see on his side / tall grass covered the hole.

When I got home my diif magnet looked like yours after ~60mi drive home, I flushed diff w/ a few qts of oil just to sweep out the crud, then some cheap diff juice until I did a FAS & spent enough time to notice the bent shell.

That washer-thing floating around is weird but the crud on the magnet isn’t too crazy but I bet it has something to do with the vibes esp if they aren’t that typical ~35 MPH one the RR does when you need to adjust your preload.
 
Joined
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Messages
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IDK what that near-washer piece is, but I bent the shell & the inner PS driveshaft wore the splines into the spider gear & eventually or right away my spider gear portion cracked into big chunks but I drove on it for ~500mi before I bought a whole brand new e-lock diff that someone traded into Slee (mini-truckers like them for RR diffs, so I was told)

It took a while for me to realize I bent the shell, but then when I measured I was about 1/2” off from a hard drop my passenger didn’t see on his side / tall grass covered the hole.

When I got home my diif magnet looked like yours after ~60mi drive home, I flushed diff w/ a few qts of oil just to sweep out the crud, then some cheap diff juice until I did a FAS & spent enough time to notice the bent shell.

That washer-thing floating around is weird but the crud on the magnet isn’t too crazy but I bet it has something to do with the vibes esp if they aren’t that typical ~35 MPH one the RR does when you need to adjust your preload.
Yeah i've had that 35-40mph vibe too, then more recently a bit higher speed one. Anyway I'm going to have to pull it and have a look. That washer thing is like semi-spherical, shiny on the inner surface and dull on outside with a small divot attached in the center (if that makes sense). Some sort of weird metal to metal spalling going on maybe?

Thanks for the reply.
 

LINUS

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That thing kind of looks like when too long a bolt / stud is cranked into some casing & it takes the weaker case metal & pushes a circle like a paper-punch, but I can’t think of any thin steel shim-like material that would be in the diff —— so I’m pure guessing on that.

Like I said, my diff was destroyed & so new (I was on a timeline, no time to source a full used axle) -shell & new 3rd member was my only choice.
 
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That thing kind of looks like when too long a bolt / stud is cranked into some casing & it takes the weaker case metal & pushes a circle like a paper-punch, but I can’t think of any thin steel shim-like material that would be in the diff —— so I’m pure guessing on that.

Like I said, my diff was destroyed & so new (I was on a timeline, no time to source a full used axle) -shell & new 3rd member was my only choice.
Yeah be interesting. Have to go pull off the axles and take a look...
 
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If you did a recent oil change and saw nothing unusual on the magnet, I'd pull it and take a look ASAP. Something is going on and it's going to get more expensive if you wait.
 

bpenn1980

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When I was baselining my truck (93k at the time) I drained the front diff and got lots of metal out including a round plate like you have there. The gear oil in the front diff had never been changed though, so those chips turned out to be a non-issue and never returned.

Assuming this isnt the first time the diff has been drained on your truck, I'd assume something is going on that needs attention.
 
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Been discussed before. The consensus is that the small disc of metal is what's left over from the original tapping of the threaded holes of the axle housing (in Japan) before the housing is assembled to the vehicle. When the taps punch though the other side of the hole sometimes that little disc is formed and pops out. Hence a magnet on the drain plug to catch that and any other ferrous debris from the manufacturing process or wearing in.

A couple years ago I found the same from the diff of a 1995 FZJ80 that appeared to have the original gear oil (fill and drain plugs never turned).
 
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When I was baselining my truck (93k at the time) I drained the front diff and got lots of metal out including a round plate like you have there. The gear oil in the front diff had never been changed though, so those chips turned out to be a non-issue and never returned.

Assuming this isnt the first time the diff has been drained on your truck, I'd assume something is going on that needs attention.
OK that's interesting. I wonder if the plate was there before and the synthetic oil loosened things up so they were caught by the magnet
 
Joined
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Messages
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Been discussed before. The consensus is that the small disc of metal is what's left over from the original tapping of the threaded holes of the axle housing (in Japan) before the housing is assembled to the vehicle. When the taps punch though the other side of the hole sometimes that little disc is formed and pops out. Hence a magnet on the drain plug to catch that and any other ferrous debris from the manufacturing process or wearing in.

A couple years ago I found the same from the diff of a 1995 FZJ80 that appeared to have the original gear oil (fill and drain plugs never turned).
Problem Solved! I tapped the breather hole for a larger fitting! Forgot all about that! Thanks ;) Fortunately I just finished taking off the swivels and hadn't pulled the 3rd. Whew!
 
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Got more details on tapping the threaded hole, thread size/type (Metric, SAE, BSPT) and the fitting you used?
 
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Got more details on tapping the threaded hole, thread size/type (Metric, SAE, BSPT) and the fitting you used?
I used a brass bulkhead fitting Greenline Part No. G0808BBH-02-02. It is designed to screw into a tank and provide a 1/8" FNPT cplg thread. Not sure what the female thread was I drilled and tapped into the differential housing to mount the bulkhead fitting but it was a std UNC screw thread I believe. Some teflon tape and a snug fit ensured it wouldn't move or leak. Onto this I installed a 90deg elbow Greenline Part No. G21B90-013-025 with 1/8"MNPT on one side and 1/4" hose barb on the other. To joint both differential vent lines I used a G20BT-025 hose tee. Hose was std 1/4" rubber fuel line hose Greenline No. G611-025 1/4".
G21B90.jpg
G0808BBH.jpg
 
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Do you have the (smallest) ID of the brass pipe fitting ie: compared to the OEM fitting?
 
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Do you have the (smallest) ID of the brass pipe fitting ie: compared to the OEM fitting?
Best estimate: OEM fitting ID = 2.5mm versus 1/8" NPT Brass ID = 5mm, so about 4 times the area. Hydraulic friction varies by the 5th power of the diameter so 1/32nd as much flow resistance per unit length if I recall my 2nd year fluid dynamics correctly.

Here's a pic...
IMG_0517.JPG
 
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OK, thanks
 

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