DIY VL●OG: Lexus GX470/LX470 Toyota 4Runner/Tacoma/FJ Cruiser Front & Rear Diff and Transfer Cas
Just as important as engine oil, your differential and transfer case fluids are there to keep those gears grinding smoothly(no pun intended). Don't be surprised to find metal dust sludge from the magnetic drain plugs, as they truly do grind constantly, which is why this is just as crucial as any other fluid in your vehicle. It's truly a very easy task, just make sure you do it on a level road, and if you fit underneath the stock height of your truck like me, then you save yourself the extra 5 minutes of jacking it up.
All you need is a gear oil pump, and no you can't reuse one if it has had a different fluid in it. It wouldn't hurt having extra fill or drain plug bolts too since its not that uncommon to strip those things when doing this. And new crush gaskets are a must if you don't want them to leak.
Front Filler Plug 90341-18032
Front Drain Plug 90341-24014
Rear Filler Plug 90341-18006
Rear Drain Plug 90341-18057
Crush Gasket Part Numbers:
Rear and Front Differential 12157-10010 (3x)
Front Differential 90430-24003
Transfer Case 90430-18008 (2x)
After careful research of oil products, I decided to use Amsoil Severe Gear 75W-90 gear oil for both differential and transfer case. I was quite impressed with the reviews it had, and didn't see any advantage paying the price of OEM.
All-in-all, you'll be able to tell a difference especially if it has never been done before.