I don't have the time to order Redline MT90 tranny fluid/oil at the moment, so I was wondering what tranny fluid/oi that I can get from Kragen, Autozone, etc. should work well... I've read to use 75w-90, but synthetic or no?

Basically, just any tranny fluid/oil that I am able to get from any of those chain stores...

 

Any 75W90 synthetic will work well, I think people tend to over analyze the situation by saying "must be redline" or "must be royal purple". Most of these cars probably still have the original fluid from when the cars left the factory.

 

Synthetic - YES
It's far better in our transmissions.
75w-90
I don't believe the brand matters. (Mobil 1, Redline, Royal Purple, etc.)

I don't know about 75w-140. - Anybody have any information on 75w-140?

 

Is there any performance shops in your area? I thought i'd have to order mt-90 too but i found it locally. Later on i realized there is a few places that have it. Actual perfomance shops most likely will have it, also smaller places that supply shops(lots of delivery p/u trucks) most likely will have it. Sorry for not answering you question, but that **** rocks.

 

75w-140 is too heavy for the rx-7 tranny will cause rough shifting and also loss of hp due to the weight of the oil.

 

I don't know, that's intriguing- you gotta figure, synthetics are generally "thinner" looking/ feeling than the conventional 75W-90 gear oil, and, at 75-140 you'd still be at a base of 75W, it shouldn't act like 140 until the temps force it to, right...

 

What kind of tranny fluid should a 500 rwhp Rx-7 use?

 

.

 

Period?

 

I dont mean to be rude but 500 hp fc's are quite rare and if you have the money and/or the skill to build a motor like that i hope to god you know what type of transmission fluid to run or your mechanic should.

 

Well right now I'm using royal purple 75w-90. I'm always curious and constantly trying to learn more. I asked to see if there has been research conducted or personel experiences in which suggest I should use a different type of tranny fluid.

 

I think you are fine with either royal purple or redline. My '81 had the original clutch and gear oil and when I removed the clutch it was dust and the gear oil was thick and gross looking and smelled terrible. I think everything should smell like gasoline.

 

Has anyone tried GM synchromesh in our trannies? I hear good stuff about it from a lot of car people.

 

There was a thread a long time ago, where it was discussed that synthetics were bad for the brass in our trannies. Now I dont have any factual evidence of it, but maybe a search will yeild answers....

So I am gonna search.

 

https://www.rx7club.com/showthread.p...+transmissions

 

I was erasing my post

 

Well- I just had to try the 75w-140 synthetic.

The syncros, gears & bearings seem to like it. They are much quieter.
BUT - shift effort is stiffer.

Next time I will go back to 75w-90 synthetic.

 

I use GM syncromesh in the 4 RX-7's I've had. Cured a 3rd gear syncro grind that had redline in it..great stuff and avaliable at any GM dealer. I've heard that pennzoil syncromesh is the same thing but cheaper. I can't find it around here, though..