Rear Diff Leak from Drain Plug Only

EDIT: Fill plug not drain plug.

Was under the truck to rotate the tires yesterday and noticed a small droplet of oil on the bottom of my pumpkin. After further inspection, it’s quite obvious that the diff is leaking from the drain plug. Nowhere else do I see leaking.

This truck only has 23K and it’s all been road driving. No diff service. I have an appointment in a few days to get my drivers front strut replaced and my glitchy speedo needle looked at. I will definitely be adding this to the list.

In the meantime, any ideas what I would be looking for? I’m going to inspect the breath valve when I get home. I am surprised at the issues I’ve run into on this new Tacoma.

 

Toyota uses a crush washer for the diffs, although you may not have serviced it, the dealership may have serviced or changed fluids. Its a $3 crush washer and cannot be reused. Diff shouldnt be leaking from there anyway as thats the fill line and if its leaking out that means its overfilled. Take that out, replace the washer, ensure the fluid is good (color) and put the fill plug back in. Should be good to go otherwise. if the fluid is black or metallic, contact the dealer (at 23k miles) and notify them immediately and I would either change fluid and drive in (save the fluid for proof to dealership) or tow directly to dealership.

 

Remove the fill plug and replace the seal.

The differential bearings are splash lubed. Meaning, it’s like a hurricane in there at 70mph.
Lube can get on the end of the plug and seal out.

Really hard to tell the origination of the leak with that pic. Take it to the dealer if you need to

 

I have never had this truck to the dealer to be serviced. That’s what has me scratching my head. Unless the crush washer was defective from the factory.

 

Also get a rag and wipe this down. Clean off the old gear oil to ensure this was the issue. Did you inspect the diff prior? Was there no oil or is this your first time looking at it?

 

Snug it down and brake clean the area. Watch to see if it still leaks.

 

That's the fill plug, not the drain plug. The drain plug is in the bottom right protected by the flange. It's pretty difficult to get a leak out of the fill plug unless it's really loose or the crush washer has failed and you've spent some time on an incline or you've submerged the diff and it's pressurized.

It's pretty easy to pop the fill plug off and take a look but if it's going to the dealer for wrork anyways just ask them to look at it.

 

First time looking at it since I did my last 5K mile service. I would have noticed it then as I jack up the rear end using the diff.

I’m going to leave the oil there so the dealer can see it in a few days.

 

Thanks. I meant to say fill plug!

 

Lots of good advice here, but the first thing I would do is put a torque wrench on the fill plug and see what it is torqued at. It may not have been torqued to specs but tight enough to prevent a leak. After 23k miles of driving, it may have vibrated itself loose just enough to leak.

Best of luck and be sure to let us know how it turns out.

 

I would remove the plug and check the oil level, if all is good, simply replace the gasket and replace the fill plug to the correct torque spec.

 

Agreed, Id remove it and check the level, check the crush washer then torque it back down to spec. Unless you are hoping to leave everything as is for evidence at the dealership. Personally I like doing all my own maintenance. I have had issues with mechanics and techs either not tightening or overtightening bolts and nuts. Recently had to remove a front differential drain plug that was stripped by the dealer.

 

Trust me, I’ve kept all of my vehicles out of the dealership for over 15 years. I HATE going to the dealership. It’s a waste of an entire day for work I could do myself. I just want to take advantage of the warranty while I have it. But since these checks are so easy, I think I will go accomplish them regardless.

I am going to go down and check the torque because that’s honestly what the dealer would do anyway.

 

Last time I took my wife's Honda into the dealer for a tire balance and engine oil change, I found the oil drain plug was torqued on so tight I almost rounded off the head of the bolt the next time I changed the engine oil. I was kicking myself because I've learned my lesson before never to have a dealership mess with my engine oil.

 

I recently dropped the front skid plates to change out the rack and pinion and thought I should check the fluid in the front diff as well, this is what I found.

 

Well I feel like a complete idiot. Here I am trusting Toyota so much I automatically ruled out a loose nut.

I crawled under my truck tonight and the fill plug was so loose I could take it off with my fingers!!

I took it off and stuck my finger in the diff. When I removed it, I had oil on it. Please let me know if there is a better way to check diff fluids. I believe the factory manual says to fill to just below the fill hole. That checked out with the finger test.

Fortunately my drain plug was tight. I torqued my fill plug down with a few extra ugga duggas. It just blows my mind that it was that loose.

 

Diff is usually filled until the fluid starts to trickle out of the bottom of the fill hole.

 

I have all the fluid for a front and rear change. I might just do it early - I’ve heard too many stories of these trucks coming low from the factory anyway. Plus, I’ve got a long trip coming up in June.

 

can’t hurt……glad you sorted it out

 

Fill it up until it just starts coming out the fill hole. Replace fill plug. Done.
Occasionally, I might wait 5 mins or so before replacing the drain plug. Just to give the fluid time to settle down.
Then I'll make sure the fluid is topped off or full.

But honestly, most of the time, I fill it until it start coming out the the fill port, stick the plug in, and call it done.
I hate the smell of gear oil. The less time I'm "playing in it", The better off I am.