If you haven`t already I would buy the replacements before you go any farther. My front diff plug was stripped. I had to weld an allen wrench to it and then it broke free. Have the replacement ready

 

Soaking the plug with rust remover won't accomplish anything - the metal plug gasket is outboard of the threads, so no rust remover will penetrate past the gasket, and the threads themselves are perpetually soaked with gear oil, so external rust doesn't play any part in the 'stuck' plug.

These plugs were very tight from the factory, and may have had their driving recess stripped out by someone attempting to us a 3/8" hex driver to unscrew them, rather than the correct 10mm hex driver. The 3/8" driver might appear to fit, but it's actually undersize for a 10mm driving recess and will almost inevitably strip out the plug.

So the first question is, do you have a 10mm male hex driver with a 3/8" square drive that can be turned with a ratchet wrench? If so, carefully clean any rust or mud out of the fill plug's driving recess, insert the hex driver, give it 5 sharp blows with a steel hammer, then attach a ratchet wrench and try to unscrew the plug.

If the plug's driving recess is hopelessly stripped, you'll need to get an T60 Torx male driver bit that's just slightly oversize for the stripped hole in the plug. Carefully hammer the Torx bit into the plug, then unscrew. Make sure you have a new replacement fill plug on hand.

Rather than replacing the fill plug with the same Toyota part, use a Lexus fill plug that has a male hex like a regular bolt, and not the female hex recess of the original plug.

 

Air Impact Hammer Kit

Amazing deals on this Air Impact Hammer at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

I like Sanderhawk's idea. Have an Allen wrench welded to the old plug so a box end wrench can be used. The heat from the welding will help with freeing the plug too. Purchase the Lexus plug that FJtest posted as a replacement. I'd be leary of using an air hammer on the old plug and potentially damaging the sealing surface on the diff.

 

You guys are making this WAY more difficult than it needs to be.

Just get a cheap Torx T60 driver from Amazon ($10), place it against the 'stripped' hex driving recess on the filler plug, give it a few firm taps with a hammer to force it into the plug, and unscrew the plug. Literally 30 seconds and the plug is out. I've used this technique multiple times on stripped drain plugs and damaged socket-head cap screws, and it's 100% effective.

No welding, no cutting a hardened steel Allen key, no risky heating of the diff housing with a torch, no trying to get a pneumatic chisel into a hard-to-access location. $10 and 30 seconds and you're done.

Here's the $10 T60 bit from Amazon:

Here's the width across the 'points' of a 10mm hex driver (this will be the diameter of the stripped hole in the plug)

Here's the width across the 'points' of a T60 driver bit. There will be about 1.5mm of interference-fit, which will easily unscrew even the most stubborn plug. The hardened-steel Torx bit will easily broach a Torx recess in the soft steel plug.

10mm hex and T60 bits side-by-side.

 

Ready made easy out, I like the idea.

 

Place chisel at 2 o'clock and it's off in one squirt.

 

Looks like he said rear diff bolts w/ the 24mm bolts, not front. Good advice for front though.

I’ve had bolts swell and loose shape, rust and merge to frames etc. made worse by rust converters being applied with out properly removing rust. It’s likely that your bolt head and washer merged to the axle. With a process of soaking with pb blaster, giving some soft to medium wacks with a hammer, and scoring the visible edges of the bolt with a stiff wire brush, you’ll expose enough surface area to allow PB to do its thing and bring back the shape of the edges of the bolt enough to get it free. Might have to rinse and repeat a few times but it can be done without heat.

As mentioned, the threads won’t be rusty so once you break the rust seal it will come out easily.

Always a good idea to remove the fill plug first so you don’t end with an empty diff you can’t fill!