Differentials, Gear Box, and T-Case Gasket info needed!

Hey everyone,

Im about to change out the differential, t-case, and gear box oils on my 02 tacoma 4x4. I understand you have to replace the gaskets for the drain and fill plugs on each of these. My brother is a Toyota master tech, and I asked for him to get me gaskets for the drain and fill plugs on each of these, I received 4 that look like regular washers, and 4 that moreso resemble key rings, i.e. much thinner.

I watched some DIY videos on changing out these fluids and it seemed like both the drain plug and fill plug utilized the flat looking washer. Can anyone that has already done this shed some light on this, id hate to get into this and realize i don't have the right gaskets and pull an exxon valdez in my garage/driveway

 

The drain plug gaskets are basically an aluminum washer with a very thin edge - the one on the right:



I'm sure the other one is for something, but I'm not sure what.

 

I asked my brother and i put the crush washers on the drain plugs like he advised, since the drain plug is actually holding the oil in and needs a tighter fit. I did this a week ago and i notice no leaks from anywhere. When I took the old ones off, they all looked like crush washers. The only exception was the front differential drain plug which was much much bigger and had a copper gasket, which i didn't replace. just sharing for anyone else who may have been wondering.