Why is my front diff drain plug always so tight

I changed the front diff. fluid this morning and the drain plug was tighter than dicks hatband. The last time I changed it I had to use some heat and a cold chisel on the plug to get it loose. I put on a new one using a new washer and torqued it. This time it was STILL tights as hell but it only took a breaker bar to get it loose. I think someone is crawling under my truck at night with an impact gun and messing with me LOL.

 

Pretty common occurrence across all the Toyotas that use these plugs and washer. Have you tried using anti-seize?

 

Wet torque and dry torque are very different numbers. If you torque it to the specs, you'd better clean those threads free of any lube. Not happening so look for wet specs.

 

Really? This is a thing? I never knew!

 

https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html

 

The things I didn't/don't know would outnumber the grains of sand on a beach.

 

For real! I just changed mine last week on both the tundra and sequoia. Broke a socket adapter and about twisted a hex key in half before they budged! I did the tundra's front diff last but didn't torque all the way to spec - just snugged it up until I was sure it wasn't weeping. New gaskets both times, and it was STILL tight! I ordered some 1/2" drive hex head sockets for next time.

 

Ya, those will be significantly different numbers. Not to bring up a can of worms, but if you decide to put antiseize on your spark plugs, the factory torque spec is no longer valid and you can strip the heads if you try. Factory spec is for a dry thread. I've seen other bolts strip threads or shear from using dry torque specs on wet threads.

 

You could always switch to the Lexus plugs to get away from the hex plugs. I use the german torque spec on mine and don't see any leaks.

You have to get them from a Lexus dealer, not Toyota.

Drain plug: 90341-24016
Fill plug: 90341-18060

 

I KNEW somebody would have that part number! I couldn't find it; forgot that it was a Lexus part. Thanks!

 

My beach is bigger than your beach.

 

Don't be such a beach.

 

SOB, I learned something on a Friday. I did put in a hex head Lexus drain plug this time.

 

I’ve had much better luck since buying a quality 10mm 1/2” drive Allen socket.

It’s still tight, but it never feels like I’m gonna strip the bolt hole. Feels more like I’m gonna flip the truck over if it were any tighter though!

Honestly, I’m surprised nobody has just crammed an earplug into the fill hole…

 

Those sound like some big ear plugs, asking for a friend, where could I get some?

 

On a separate note the rear diff is just a breeze to drain and fill and those plugs are always tight but not bust a nut tight. I used the squeeze bags of gear lube on the rear and not pump needed.

 

Is the diff housing aluminum? Wondering if the aluminum housing and steel bolt could be a factor.

 

All you need is a quality 10mm 1/2" socket and a 24" long breaker bar. I've never had an issue.

 

100% correct. But still, that bolt makes us look like a wife trying to open a pickle jar sometimes.

 

I just had front,rear, and transfer done but my question is why do they all need to be done at the same time? Wouldn’t the rear diff fluid be in the worse shape by not using 4wd that often?

 

Shit, I completely forgot/spaced out this necessity. I guess stumbling upon 2 different threads on changing gear oil in diffs and transfer case, in last two days is a sign. 6 quarts ought to do it, right?

 

Should but I would grab a 7th just in case

 

I stripped out the drain plug on the FJ - had to drill it and use an extractor. Switched to the lexus hex bolt for that one. Why did toyota think the allen plugs were a good idea?

 

Dealer service $$$.

 

At that point you want to inspect it anyway. For most people it's piece of mind, and you get to find out that your plugs may or may not strip lol

 

My front diff oil looked great and was still purple (used RP first time) but the drain plug magnet had a little metal dirt stuck to it but not much really. The rear diff fluid looked dirty but not bad either and the rear drain mag had little to no dirt on it. This time I just put valvoline in both and used the squeeze bags.

 

So, double check the manual, but I seem to recall the front needing to be done around the same mileage as the rear, but the t case being good for longer intervals. The rear diff has more than twice the oil capacity as the front diff, which helps fluid longevity and keeps temps lower than a lower capacity diff, even with the increased load. The nature of the ring and pinion does cause fluid to shear more quickly than gears and chains like the transfer case.

That said, I do the rear diff once a year mostly because the limited slip additive shears down that quickly (aftermarket Auburn pro) and check the front diff and transfer case while I’m there. I usually just change them while I’m at it.

 

To add to this, torque specs are relying on a ton of assumptions, wet, dry, are the threads clean, are the threads in good shape, different lubricates can affect coefficient of friction, etc. etc. Realistically you're lucky if two fasteners have the same clamping force within 25% at the same torque and same "idealized" environment. This is why things like ARPs are used to try and more tightly control variables, and even then you have a pretty significant variance in clamp load.

Not to say you shouldn't torque things, but there is a lot of shit going on for something so simple and your resultant loads can be all over the place, which makes torque specs kind of a joke in my opinion. They are driven by hitting a minimum load usually, and due to the variance you may end up with a much higher loading than you expect.

 

Age. Look at service intervals on lots of things. It’s often by miles, or time, whichever comes first. The rear will certainly see more stress than the front, but the oil up there is still getting old and the likelihood of moisture contamination increases with time.

That said, I drive 25K miles per year. Change all three gearboxes annually.