Doe's anybody use synthetic tranny fluid? My mechanic who has over 20 years working with rx 7 says that it's not good and causes problems in my 86 rx7 na. Doe's anyone know if this is true? They sell all kinds of synthetic tranny fuid for my 2nd gen.

 

I don't think I've ever heard that it will hurt anything, just that it's not necessary unless you're doing trackdays/autocross all the time [assuming you change it at regular intervals]

 

Synthetic transmission lube will not harm it. The FC transmission is no different from any other gear box, so it'll have no issue with synthetics. What he's probably referring to is using synthetic oil in the engine. That has been stated before to cause excessive deposits since the rotary was not designed to burn it. Whether that's true or not, I don't know. Not enough research has been done on it, and there's a huge debate on it that I'm sure will spark alot of controversy. I say to be safe, stay with dino oil in the engine. Gear lube and diff lube can be synthetic all day long. I use Amsoil and it works great.

 

I filled mine with Redline MT-90, which is a synthetic GL-4 transmission oil. I have used it in many other cars and it has performed well in all of them. So far it has been great in my FC

Just don't use a GL-5 (many synthetic gear oils are GL-5 so check CAREFULLY) and you will be fine. Personally I recommend MT-90 for the job.

Also, check and change your rear diff fluid at the same time, it tends to get neglected.

 

^ +1
I've always put Redline MT90 in the transmission and Redline's Multi VIS gear oil in the rear end. I've owned 2 RX7's over the past 10 years and used both as DD's and never had a problem.

 

I used redline heavy shockproof for the diff. Mine was whining BADLY due to running on virtually no fluid. When I drained what was in there (a little over 1 cup) I found several partial teeth in the fluid. Since it was just a normal N/A open diff and I don't count on it for daily transportation I tracked down the thickest fluid I could put in there to try and make up for the excessive backlash, fixed the leak (bad axle seals) and went with it. 250km with 2 auto-x sessions later it hasn't blown up and is whisper quiet. I doubt it will last very long but hopefully it will get me through the season and into next year when I have more money in the racing budget

 

Personally I just started using Royal Purple Synchromax in the transmission and it seems to shift as smooth as a knife through butter. I was concerned about the same thing, potential damage, and after alot of research I came across a few factors to take into consideration. One being the weather in relation to the fluid thickness. I chose synchromax because its advertised to work with soft metals and because I live in Texas where it is hot. In this forum there are some who commented that Redline works better in cooler climates and RP or thicker oils work better in a hot climate. I have no clue if this is 100% as anything on the internet seldom is, but yeah no complaints thus far. I'll see what happens and will let you know if anything goes wrong.

 

I don't know why, but "regular" mechanics tend to think that because the rx7 has a rotary, that the entire car is somehow different in the basic operation principles and how to work on it than any other car.

Synthetic will do fine in the trans, however it won't necessarily cure an old worn out trans that you're already having issues with.

 

i have royal purple in the trans on my 88 10AE and it shifts well, has no leaks and has been a reliable fluid for me. i prefer redline MT90 over royal purple but i have had good results using both.