I got a series 8 rx7 3rd gen, i want to flush out all of the old engine oil included from the torgue conveter. My question is how many litres does the gearbox hold. As i pouring royal purple ATF oil in it. My mates put it in his rx7 and his gearbox flew. I don't know how to pull the rest of the fluid from the torgue converter but is it easy to do i got this section tell that i can put down the gear stick and pump oil out from there is that where the rest of fluid is.

And last the diff how much oil do i need for it,

 

Huh? "I want to flush out all the old engine oil from the torgue [sic} converter"? I'm not sure what you're asking. The automatic transmission DOES NOT contain engine oil. It DOES contain ATF.
As for how to do it and how much it will take...check the Factory Service manual. If you haven't already, download a copy from the 3rd Gen. stickys. It will also tell you the differential capacity.