One thing that is very important is not to over fill. You must check the fluid level on a level surface and not when the vehicle is on jack stands or ramps. Over filling will cause the seal to leak.I know this is an old thread, but like me there is always somebody new doing the rear axle, and transfer case drain/refill. So here's my take as of 9/11/2019: I went with the Toyota recommended 80-90 conventional gear oil. I used Valvoline 1qt. container, and an Atwood gear oil pump from Walmart. https://www.walmart.com/ip/Attwood-Gear-Lube-Pump/16351021 which worked perfectly, and only cost $4.87. The only issue with it is the pick-up tube does not reach all the way to the bottom of the gear oil bottle. I fixed that issue by getting a piece of vinyl tubing that fits the outside of the pump where the supplied pick-up tube goes. This allowed me to reach all the way to the bottom of the bottle. This little pump even has a cap that screws onto the output end fitting which helps keep oil from leaking out of the tubing when you done pumping.
I didn't have any problem removing any of the 4 plugs. I used a 3/8" drive 10mm hex socket on a 3/8" ratchet with a 2ft cheater pipe over the ratchet handle to break the plugs free. I was able to use the socket on the 3/8"ratchet on the one plug that is has a tight clearance where others needed to use a cut off hex wrench. Even my 3/8" torque wrench fit the tight spot. I bought new crush washers for all the plugs from a Toyota dealer. I highly recommend replacing the crush washers with new ones even though you may be able to reuse the old ones. They were $1.64ea. Cheap insurance IMO. Part # 12157-10010. All 4 plugs use the same crush washer.
In conclusion: This job turned out to be easier than I originally thought. I was lucky enough to have the use of a friends vehicle hoist which makes this job much easier than using jack stands and "flatbacking" the wrenching. I was able to do both fills with one qt. of oil although I bought two in case I spilled some which is probably a good idea as you never know. If you don't have a 3/8" dr. 10 mm hex socket, Home Depot has a cheap one. https://www.homedepot.com/p/Husky-3-8-in-Drive-10-mm-Hex-Bit-Socket-H3DHBS10MM/202913545
View attachment 145354
View attachment 145355