Rear Diff Leak

A few days ago I changed the oil in my front diff, rear diff and transfer case on my 08 Tacoma. Before changing the rear diff, I had noticed a slight leak at the drain plug and some oil pooling under the truck. The rear diff was very dirty/grimy as well. So when I changed the oil in the rear diff, I put in a new drain plug and crush washer and torqued to specs. It has been a week or so since I changed the oil and while there isn’t a large amount of oil leaking out, after the truck sits cold for a while, a small amount of oil will still slowly drip from the drain plug. Any thoughts on what to do? Thank you!

 

There are a few of options.

Some require draining the diff once again.
At least one doesn’t. And that one is surely going to bring on the hate.
But hey, it’s an option. Maybe not the best one, but a last one maybe? (It’s option 4 below)

1. Try to see if you can snug it up a little. Don’t crank on it too hard.
You don’t want to strip it. But maybe it just needs to be cranked down a smidge more?

2. Remove plug and inspect mating surfaces.
Make sure there isn’t an old gasket stuck to the diff.
Clean surfaces good. Replace with new gasket washer.
Tighten it until you think it’s good and tight, then check it with a TQ wrench.


3. Use Thread Sealer
https://www.permatex.com/products/t...nts/permatex-high-temperature-thread-sealant/

4. Use an RTV gasket maker and “fill” the area around the drain plug.
Yes, this is absolutely a “Shoddy Fix” and is not at all considered right or correct.
But there have been guys fix their timing cover leaks this way. Mostly because it a big job, and smearing RTV is much easier.

 

Pull fill plug
Top off
Replace crush washer ($1)

Edit: Is the drain plug leaking or the fill plug?

 

That’s also an option.
Do nothing and add fluid as needed.
I’ve done it myself.

 

Just throwing it out there if it’s not the plugs. It could be the pinion seal and it’s working back there when you driving.

 

double check torque spec
clean with brakleen and re-evaluate
these housings can crack and leak but usually look in way worse shape when they do that

 

The threads are leaking. Like a plumbing fixture. Remove the plug and put Teflon tape or thread sealant flip crush washer over or replace tighten and let dry over night if using thread sealant
Leak will stop. Happens all the time

 

He said drain plug and if you look at his pic you can see the oil dripping from the low point of the drain plug boss.

 

OP, these fellas have provided some good advice here for consideration.

Touching on TnShooter's #2 option, the fact that you've changed both the plug and washer would make me question the integrity of the mating surface of the diff drain plug boss, so be sure nothing is dorked up with that. Also, as @TnShooter alluded to with option #4 being a shoddy fix, I can't help but think of option #3 the same as well and if given the pick between those two I'm probably going with option #4 over #3. To me, the seal is suppose to be happening at the mating faces, not the threads, so I'd be wanting to apply the BAND-AID fix in that proximity. Either way, both would work and as they say, "desperate times call for desperate measures."

 

These are not NPT (pipe) threads that form a seal at the threads, they are straight threads and provide no seal.

 

I didn’t realize it was the drain plug
It looked like the fill plug was leaking in the pic.
Even though the treads are not sealing this same thing happened to my on one of my other trucks a Nissan Frontier . I cleaned the surface of the plug , cleaned the surface of where it mates at the diff and put a new crush washer and it still leaked. Although my issue was on the fill plug only. My solution was thread sealant and letting it dry over night .

 

Given how little fluid is in the rear diff and the ease of access, for me it’s a no-brainer what I’d do. Buy a new plug and crush washer. Drain the diff, wipe the drain hole dry and inspect it and the plug closely with a flashlight. Mating surfaces and threads. See if there’s a doubled up crush washer. Hope that you find something obvious. Install new drain plug and washer and refill. Check the torque a few times. Maybe your wrench is out of calibration.

 

Yeah I hear ya. Gotta do, what you gotta do. Sounds like you went with option #3 from TnShooter's post. Plus, sometimes there comes a point with leaks where you're just over it and ready to move the F on with life...so out comes the sealant.

 

Thank you for the input! This is all very helpful. I did already try torquing the drain plug down again and it didn’t seem to help and I’m 99% sure the old gasket wasn’t left on. I cleaned everything off really good and inspected closely before putting the plug back in. I’m curious to try the thread sealer and see if that helps. I’m going to replace the crush washer again too but I did have a question about that to make sure I installed it right the first time. I put the flat side facing the bolt head (curved side facing the drain hole). Is this correct? Thank you all again for your help! I don’t know what I’d do without this community.

 

Flat side facing the plug, yep.

 

Sometimes an old crush washer gets stuck on the diff housing and you'll need to pry it off with a screw driver. It would create a leak similar to this.

 

Had same happen on a Sequoia I had. Somehow, when the plug was removed I nicked the mating surface on the diff. side. I could run my finger on the surface and feel the knick, small, sharp. I smoothed the surface with a fine file. I am not sure if this procedure is recommended or not, but it worked.

Initially, I thought the issue was the new crush washer or plug, I ran the truck for a week waiting for the new washer and plug. When I drained the diff after a week I planned to reuse the fluid. The fluid came out so nasty again that I replaced it.

Good luck!

 

OP.....as a thought.....

You could try a fine wet/dry sandpaper to clean/polish the gasket surface. Just making sure all is clean and without nicks or burrs.

 

Teflon tape.

 

Well, I tried most of these suggestions (new washer, new plug, cleaned/lightly sanded the mating surface, thread sealant) and there is still a leak.

Would you recommend I try tightening the nuts on the diff? I’ve read a few threads of guys causing more issues by doing this so that’s why I’m asking. If I researched correctly, I believe my 08 V6 off road should call for 18 ft lbs on the rear diff nuts.

If you have any other suggestions, please let me know. Thanks!