Rear Diff Leaking

So recently I changed my rear diff fluid because I didn't know when it was last done. About two weeks after I did that, I noticed the area around the fill plug was slightly wet. I realized I reused the crush washer, so I ordered a new one and put it on hoping that was the reason my diff was leaking. Fast forward another 2 weeks or so. Didn't think about it until today when I noticed it was still leaking the same as before... I was trying to do some research but I'm not sure what the issue could be. I also noticed today what appears to be a small leak on the front bottom right side of the diff as well. When I put on the new crush washer there was barely any fluid missing. Could I have over filled it and there's too much pressure in there or could the probable cause be a clogged breather? Any help is much appreciated. Trucks got 191k for reference.

 

That looks more like residue than an active leak, did you clean it off good with brake cleaner and see if it returned?

 

Hit with break cleaner (and a power washer for good measure)... That's how I noticed it returned. It doesn't feel wet to the touch, it's more like it was wet and then dried. I just cant imagine it leaked a little and then stopped

 

Through capillary action that oil is going to spread itself into every nook and cranny evenly. It can make the amount that may have been in the space behind the head of the fill plug look greater than it would have before it started spreading out.

 

Gear oil can be very difficult to get cleaned off even with solvents, you may need to wet a rag with brake clean and wipe it all down good.

 

Just looks like it was recently changed to me. People reuse their crush washers for years with no ill effects (no saying you should, just that I doubt its an issue)

I would clean it off and see.

 

I guess I'll add this to what I originally said. The diff was bone dry until I drained/refilled it. I cleaned up the little bit I spilled, drove it around for 2 weeks or so and noticed oil had leaked about as bad as it is now. I added a new crush washer, cleaned it again, drove it for another 2-3 weeks and its now in the state it's in. I really don't think it's residual as the second time around, the area of where it leaked has increased some.

 

Good thorough explanation. Seems like it might be a very very slight leak, but to go with what you said - check the breather - it wouldn't be a bad thing to pull the rear drums and look for any signs of oil being pushed through the bearings.

If all that checks out, then maybe putting a seam of rtv around the crush washer. At least that would be proof of concept.

 

I'm a big fan of Teflon tape. Put some on the threads of the fill plug, clean the area and keep an eye on it.

 

Did you torque the plugs to spec?

 

Check the torque on the fill plug.

 

This ^ but I expect that should have been what you did many times at this point.

 

Also, remember if the plug is wet it changes the torque value. I've over tightened a lwr unit plug on an outboard and ended up crushing the crush washer... let lake water into the gear oil.

 

I agree.

The rear is Torqued to 36 ft/lb.
I use long 1/2” ratchet and a 6 point 24mm socket.
I usually tighten it until it feels “tight”, and then check it with a torque wrench.
So far it’s always “clicked” when I checked it. So it is either just right or too tight.
But mine hasn’t leaked yet. And I’ve reused the washer too.

The fill plug is “thin” on the head, and I just don’t like using a 12 point boxed end wrench.
That sucker is always super tight when I go to break it free.
I usually end up smashing my elbow or hitting myself in the head when it finally breaks free.

 

If it's not dripping where you park overnight, it's probably fine. If you have a lot of hoes and park different places every night and can't tell, well, you probably shouldn't worry about a minor diff leak.

Looks like you've got one of those rarities with an actual LSD. Did you add friction modifier?

 

I’ve been planning on pulling the drums and looking for oil (also probably need to replace the brake shoes as well LOL). I’ll also probably replace the breather as well…

 

I don’t think my wife would like me having that problem But I’ve never seen it drip anywhere
Rarities? I thought the LSD was standard on the TRD Sports… And yes I used a diff oil with the additive mixed in.

 

1. Takes 3.1 qts or until comes back out. If overfull it would have been flowing/running out rapidly
2. As others said torque it or tighten. Did you use the correct steel crush washer that crushes or the aluminum case flat one (wrong one for the rear diff).
3. I always clean the plug with brake cleaner then apply a dab of black form a gasket on bottom of threads and onto crush washer inside area by bolt.
4. Vent on diff ever been changed (one way) or the relocate done using an open style breather. Bad one can pressurize the diff and force fluid to leak out.

Just did mine with 80w-90 Lucas and same old used washer but did the above and no leaks.

 

Yup I filled it until there was just a little bit coming out.
Going to be honest, I bought a crush washer set off Amazon that said it was for the rear diff drain plug on our trucks
I'm thinking I'll probably do the breather relocation mod once I get back from my TDY in a week or so and apply some RTV to the plug (unless anyone has a better option/differing opinion)
'Preciate the advice!

If I remember, I'll try to come back and let y'all know if those two things work

 

I think only a few early years of the 2WD TRD Sport had a true LSD. Everything went to electronic LSD at some point.