Stupid question, I know, but I've searched the forum already and came up with nothing. How does one go about flushing trans fluid and putting more into it? What fluid does it call for? Any additives that I should add with said fluid such as Lucas, Synchro Mesh, etc? Any help would be greatly appreciated! Thanks!

 

What year Rx7?

The procedure is rather simple and virtually universal for manual transmissions. Drain it, but the drain plug back in. Fill it using the fill plug until fluid just starts coming out of the fill plug.

 

Always make sure you can remove the fill plug before removing the drain plug. Then follow the procedure above. I like a synthetic fluid like redline MT-90 since it's a pretty rare maintenance item.

 

http://www.aaroncake.net/RX-7/transfluid.htm

Go to this link and download the factory service manual (FSM) so that you will have the answer to this and many more questions. Your 1991 RX-7 is considered a "Series 5" (1989-1991), so use the 1989 FSM:
http://foxed.ca/index.php?page=rx7manual

Most people follow the "Unique Driving Conditions" scheduled maintenance services listed near the beginning of the factory service manual. The fluids are listed in their respective chapters, and most of them are also listed with the other technical data in Chapter 30.

If you want good shifting then I recommend a quality 75W90 synthetic oil, such as Red Line, Royal Purple, Lucas, Amsoil, or Idemitsu. If you don't care about nice shifting, then cheapie oil is just fine.

You may also want to check out this link about sloppy shifters:
http://www.mazdatrix.com/faq/shiftbsh.htm

No additives are needed for the transmission.

Not even close. My favorite was when a guy mixed low-compression and high-compression rotors in his engine and wondered why the engine was vibrating a lot.

 

Any advice for selecting auto-trans oil? Read lot about that auto needs some spezial ingriniednts that normat tranny oils dont have, is this true?

 

can't you just go to an oil change shop and get a quick tranny flush for an auto?

 

^Follow the Factory Service Manual Specifications.

And while I see the OP has an FC, for posterity for any future searches...
The FD has TWO drain plugs but only ONE fill plug. Kind of opposite of what I gleaned from Evil Aviator's how-to for the FC. Drain plugs have a magnet, make sure to clean it off. You should also re-grease the shifter ball and drain/fill the shifter resevoir with gear oil from above...but be careful.
I like NEO Synthetic 75w-90 HD.

 

If i mention I have RX7 first their like what??? and then they are: we dont know anything about that... So thats why im asking. And for the manual, I can get the right wisco etc, from there but not the actual brand and type.

 

If it's a trusted shop, sure. There is nothing particularly strange or unique about the auto transmission in an RX7.

 

I would use Redline MT90. Works great in DSM's and they're notorious for trans issues.