oh well ,looks like you should just buy a new diff with a locker and 4.88 gears, hehehe j/k

good luck man, there's not much else to do beside do what others suggested.

hammer a hex socket bit in there and back it out, then try heat, then just weld the hex socket in there, beyond that it's the same as any suck bolt, for bad for man, i hate it when it goes down like this, you thinking 20 min job and im done, next thing you know 3 days later because of a stuck bolt....not fun..best of luck!

I had the same thing happen as well, ended up getting it out with an impact after hammering the bit in there. Thankfully, the replacement from Toyota was a bolt head, so it shouldn't happen again.

I bought a new one too and it was hex just like the old one. Wonder why we got different things...

Now you've got me 2nd guessing myself, it actually may have been another hex, but a 10mm instead of the 12mm that was stock (and took forever to find a set with a 12mm hex in it). Good catch, it was different than what was stock though.

That front diff is an absolute pain. I do it every year and have nothing good to say about either bolt. This year I am going to put it on stands so I can pull down on the breaker bar with more leverage, What in the world is the rational for hex bolts on that? Something you could use a good socket on would be vastly superior

Front diff is one of those things I go to my mechanic for - he's got the lift, the tools and the patience : ) Toyota does NOT do my front diff change any longer since they 'rounded' the hex last time they did it and I had to practically force them to replace it.

I just rounded out my drain bolt on my front diff. Although not ideal I was able to use the pump for the quart bottle and put the longer hose on the inlet side. Then feed it deep into the diff thru the fill hole. I'm pretty sure I removed over a quart of oil and considering that it had probably never been done before, it's good enough for now. One thing I noticed was the oil that drained out seemed thinner than what it should be.

Reviving this thread because my front differential 12mm drain bolt is stripped. The last time I changed all of my drive train fluids I couldn't get the front diff. drain bolt out and it got stripped. I tried again today, but I started with the fill bolt which came out without a problem. I felt inside, and the fluid was low, but the fluid on the bolt and on my finger looked good. I tried again with the drain bolt without any luck, so I just topped it off with fluid and I'm not going to sweat it. I won't have to worry about it for several years and I'll just use the pump and fill method next time.

Wow, I just stripped mine on Friday. My rear diff drain plug was WAY too tight too (gotta love PO's.) I vacuumed out as much fluid as I could through the fill plug and topped it off with fresh fluid. Saving this battle for another day.

I had mine seized too. Even hitting it with the impact, impact hex sockets and 150psi did nothing.

I welded a large nut on it, and it pretty much unscrewed like a new plug after the heat.

Buying a welder just for this will nearly pay for itself.

Also, the welded bolt will help for future removal with a much better leverage

Knew I should have learned to weld. Did the same thing as you all. Rear, transfer front fill all went smoothly...then came the last one, front diff drain plug. I could tell somebody had already started on strip it. I banged a the 10 mm in and was able to get a lot of torque on it but finally started stripping it completely. So disappointed.

Only good part is the fluid still looked good so I guess I'll just leave it. Probably going to think about it every time I drive though 😩 Hate doing a half ass job.

Good grief...my turn... on the plus side I started with the rear differential then the transfer case which, thankfully, both went well. Then came the front diff, and yup, as others have done, managed to round out the drain side hex head.

Let me first start by clarifying one point that is also very conflicting when doing a search. "What size is the front differential hex head for the fill and drain plug?" It turns out that in my 1998 SR5, the fill plug is a 10mm hex while the drain plug is a 12mm hex. So logical isn't it..... NO !!

Anyway with that piece of the puzzle out of the way I then proceeded with the front diff. Started with the top as is recommended and fortunately that one came lose. But no way on the drain plug. I had presoaked it in PB Blaster and used a breaker bar but nothing going. I wished I'd tried heat but I had thought that with the fill side coming lose I wouldn't have an issue with the bottom one. So I now join the ranks of trying to figure out my next move to getting it off. Since I do not weld I don't see the 'welding a nut to the head' as an easy option for me.

In the meantime today, I tried getting a small diameter hose in the fill side to use a hand pump to suck out the old oil but the gears inside the diff wouldn't let the hose past and down to the bottom. So for now my front differential oil is not changed. Crap.

What is it about this one bottom nut that seems to always get too tight does anyone have any idea..? I had Toyota change it the last time, is it possible Toyota just has the wrong torque spec for this nut and way overtightens it I wonder? Is there some intense heat in the differential that causes the bottom bolt thread to fuse to the case?

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It's not the threads, it's the flange ring and the compression washer that fuse to the diff case. The road salt gets in there and it locks up. Anyway, that was my theory after struggling to get mine out several years ago. Since then, I have slathered that compression washer, the outside of the diff, and that flange ring on the plug with anti-seize. The threads I don't worry about as they get fluid on them. I have always gotten mine out with no issue once I started doing this. 19 years and still the factory hex plugs.

A hammer and cold chisel is old school and brutal but when you are left with no options it is very effective. Start a notch on the edge of the plug and hammer in a counterclockwise direction. Cursing helps lubricate the threads for easy removal

Come ooon man, is'nt that my we tinker on our toyota's!
All part of it, hammer n cold chisel St Runner mentioned works good,
Never seize The Durk mentioned your good forever.