Surasonac

So I originally thought my clutch was adjusted wrong because with my clutch pedal fully on the floor the car would jolt a bit when putting it into gear.
Had my mechanic take a look, he inspected the fluid and the hydraulic rod which was fully actuating. And had the car up on the ramps to check the wheels weren't moving. They were dead still. He assures me 100% the clutch is fully disengaging.

When I bought my car the syncros other than 4th gear were totally fine. Then the tranny blew up and reverse was gone.
Put a second used transmission in, put mt90 in it. Shifted perfectly for around 200 miles and now 1st gear, 4th gear and 5th gear syncros are totally fucked.

In order to avoid grinding I double clutch on those gears now which gives me a smooth shift. But I still have no clue why my car is eating transmissions for lunch. I always rev match on downshifts etc, my shifting is really good.

I know the RX8's transmissions are weak but this is ridiculous. I've seen people at 100k miles on the original transmission and no grinds at all.

NotAPreppie

Maybe your shifting really isn't that good.

UnknownJinX

You sure you used MT-90? Double checking because you have to make sure you are using a GL-4 fluid. GL-5 fluid in the trans can cause problems.

And since you bought the transmission used, see if there is any warranty on it from the yard you bought it from. Could just be bad luck and the transmission was on its way out already.

strokercharged95gt

Surasonac

Yep definitely ordered mt-90. I remember checking it was GL-4.
See here:
And this is my 5th car, never had transmission issues on any of the others. My shifting is smooth and its fine. I live in the UK where manuals are 90% of cars and you learn in manuals. Someone who is bad at shifting definitely can't perfectly rev match or double clutch 1st to 2nd smooth (out of necessity because of grinding).
Listen here: To be honest i'm starting to consider selling my RX-8. I knew it was gonna be an expensive car to own but its getting kinda stupid.
I really love my RX-8, its nice to own something unique. If it just consumed oil and fuel and didn't spring exhaust leaks and have transmissions blow up i'd certainly keep it. I have money set aside in-case it needs a rebuild.

I've done quite a few upgrades to it which makes it even better. But its starting to become a big money pit

At this point I have two choices... sell it or buy a transmission rebuild kit and hope something isn't destroying the syncros. I'm not buying another used transmission.

Surasonac

6 speed. This is exactly what i'm talking about. I guess i'm just getting unlucky with transmissions. How can yours go for 100K and my original one blow up at 39k miles. Grrrrr

Sydo

UnknownJinX

If you need another one, I would suggest looking for an S2 transmission, which is an improved design made by Mazda in-house. All you need to do is some simple wiring work(for reverse and neutral switch) and it bolts right up.

The Series 1 Aisin gearbox is known to have shift fork issues with 4th gear.

Surasonac

Yeah I heard the series 2 fits and it stronger. Thanks for explaining it. I'm an electrician so changing the wiring is no issue. I'll give it a whirl I suppose provided I can find an S2 tranny cheap enough and close enough. I'm not driving half way across the country for it haha.

EDIT: After looking around on gumtree and ebay etc there doesn't seem to be any S2 transmissions for sale unfortunately. At least not right now.

Sydo

MX5 Miata the same

Surasonac

Wait a MX5 tranny fits the 8? Surely that's hot designed for that much power?

UnknownJinX

The RX-8(especially the Series 2) share a lot of parts with NC MX-5, actually.

And the RX-8 is barely any torquier than the NC Miata. It makes 230-something horses because it revs to the moon while the Miata can't with its 4-banger.

mazdaverx7

iTrader: (6)

If you have not, ensure you have the proper freeplay in your clutch pedal. The rod is easily adjusted and a much better pedal feel will result.

With that said, both of my 8's have their original transmissions. My 04 Brilliant black is at 98k miles and I have zero issues with that trans. My 04 Nordic Greet Gt is at 134k miles and also zero issues with the trans. Redline MT90 should not hurt the trans what so ever. I think you bought a trans that was already bad or on its way out.

Surasonac

I agree with you that I mist have bought a dud, although that doesn't explain why it perfectly shifted for the first few hundred miles when I put it in. Maybe that was the MT90 hiding the issues.

Its definitely not easily adjusted. I crawled under there with the seat all the way back and there is barely enough room to get my wrench up in there. I just left it for my mechanic to check.

Loki

iTrader: (1)

Transmissions are pretty simple devices, they work forever if used correctly and not all if used incorrectly. If the previous owners of both transmissions abused them, you're inheriting the results. Your first one already had a damaged synchro when you bought it.. soo.

One other thing to consider, and it's a stretch, is whether the power plant frame (PPF) is well aligned. If it's offset, your gearbox and diff could be experiencing unexpected side forces that screw with the bearings. This wouldn't directly wreck your synchros though. Synchros die to poor fluid or poor user input.

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Surasonac

Hmm so my only choice is to either have the transmission rebuilt... which I just looked at the price of and nearly died. Or find an S2 transmission which seem to be incredibly rare, guessing since the S2 had much improved reliability that they aren't broken for parts as often. Or sell my poor RX8. Tough decisions really.
I'll have to think over this carefully.

Thanks for your help.

Loki

iTrader: (1)

I imagine the market price for an RX8 needing a new trans is pretty low, so it might make sense to roll the dice on another used S1 trans, and get your money back in the sale ( or keep the car if it makes you happy)

Surasonac

Indeed. That might be the case.
I'm compression testing my engine on sunday as i've been feeling loss of power for a few weeks now and my mechanic spotted an oil leak when he fixed my exhaust the other day. I'm hoping the rotor housing isn't warped. If it is, i'm not even going to bother fixing the transmission. I'll just sell it as is and hopefully make most of my money back.

mazdaverx7

iTrader: (6)

The rotor housings are not going to be warped. They will either be worn and flaking or corroded around a coolant seal. In regards to the transmission issue, I would source another used S1 trans. It would be best to be able to drive the car that is going to be parted to verify that the trans is good, but if that's not available, buying from a reputable seller that backs his parts would be your next best option.

If you do sell your 8, there is a high chance that you'll miss it and yearn for another. These cars are quirky but there is nothing else like an RX-8 on the road today. The way they look is mesmerizing, they handle so well and are very balanced, and their acceleration is adequate. I would personally just hang onto the car and do my best to fix the issues and enjoy the car.