So we have a first-gen RX8 trans with a 100K miles on it that I've never driven before and were doing an endurance (18 hours) race with it in September. I feel it to be the weakest link on our car, and doing the research it seems justified. We are almost out of budget, and time is slipping just as quickly looking for suggestions.

-I haven't seen an RX8 gen 2 trans for cheap CL ebay.
-I do have a jspec RX7 T2 1988 trans that I've never drive driven on my garage floor. But have not seen a thread on that direct of a swap.
-I did see a synchro kit for $700, although a trans rebuild is beyond my ability vs time I do have access that someone that can. : Manual trans.; kit includes synchronizer rings
-colins makes a cool adapter for a 350z trans but would us too over and is not out yet until next year for rx8.
-I did pick up Red Line 57104 75W140NS GL-5 for the trans per my research, and some 75/90 for the diff
-considered making every one shift at 8k max and slowly (good luck with that)

These are just notes of where my heads at, any suggestions or advice would be appreciated.

 

I would recommend the Ford XT-M5-QS manual trans fluid instead. I used to run that RL fluid, but still had problems. The Ford is a lot easier to buy locally.

I bought a full Mazda synchro kit through Motorsports recently that was a lot less than that. Assuming you must have gotten the full kit with bearings at that price, but Motorsports is likely less cost if you can pick all the parts out in the full parts diagrams.

Just take your time and don’t shock the shifts, change fluid often, is about all you can do. There are a few internal plastic pieces that a few racers used to swap out for replacement aluminum pieces. Not sure what they were or where you can get them though.

Maybe a machined fork lever or two rather than the cast ones. I think they came from the NC MX5 6 spd racers, which internally they’re mostly the same parts. So your search might lead you in that direction.

 

About that Ford Motorcraft XT-M5-QS... I have used that before in my DD and occasional Autocrosser, and it turned burnt black a year later, and I had random grinds getting into 2nd even with clutch pedal pressed all the way down.

Just my two cents. I use Motul Gear 300 and it's a lot better. This recommendation actually came from a knowledgeable Ford owner and he obviously didn't like the Motorcraft much, either.

Also, I would not use GL-5 in the trans. It's harsher on the synchros and Mazda later changed the specs to GL-4 as well.

 

Well Miata folks have neen using it for years, including the new ND. Never even heard of such a thing before. It’s a GL4 75W90 trans fluid. I’ve run most of them and never had anything turn black before.

I also ran various GL5 fluids and never had any issues with the ones I used. Just shearing all the teeth off 2nd gear drag shifting into second gear (have 5 broken S1 trans in my garage, all 2nd gear shear-offs), which isn’t an oil issue. The oil topic is always an over-rated peeing match it seems, but if that works for you then ok.

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I admit mine is an outlier, but it did happen to me. That's why I said it's my 2 cents, and it just happened that when I was talking to another Ford owner about my experience, he recommended me the Motul. YMMV.

I agree it's just a personal preference thing for the most part. The only thing I think people agree here is to not use the Royal Purple trans fluid.

 

Team I'm assuming that's Mazda motorsports? https://store.mazdamotorsports.com/w...oriesDisplay#/ ? The only part I saw when searching was shifter bushings when going through the parts list. Didn't see a diagram, unless you were suggesting that I go through a shop manual and use the numbers from there individually? I didn't spend a ton of time on the site so I'll go back if I got that all right.

So after more googling, I'm going to run GL-4. Thanks for the heads up. I like the 75w/140 temp range but oh well. Maybe we can sneak in a trans cooler.

What do you guys think if this block plate for shifting? I have 3 other drivers 2 that are rookies. http://raceroots.com/index.php/syncro-saver.html

That and making them practice shifting slowly on my sim rig in VR I suppose will help.

 

The factory trans manual along with the parts diagrams on Motorsports. You have to be in the right area. There are a lot of individual parts to dig through.

The synchro saver helps over-shifting, but only delays the inevitable wear you’re going to see on the track.

By the way, you already bumped a transmission thread recently. It’s not really helpful to keep making new threads on the same topic. In that one you started the t-stat bypass subject, then went over and started another cooling system thread. Not trying to beat you up, but somebody needs to kindly point it out. Please try to stay on topic in existing threads and please don’t start new threads without a good reason. Sometimes I need to be reminded too, so it’s something we can all be more mindful of.