Hey everyone. Im considering using an Rx-8 6-speed manual transmission for my 20B Rx-7. The engine is naturally aspirated, and should be making ~360RWHP and 240RWTQ, peaking at ~8500-9000 RPM. My concern is that all I have heard is that the rx8 trans is very weak. I will be tracking the car a fair amount, and Im sure the occasional trip to the drag strip as well. Id like feedback from owners who have forced induction cars making a decent amount of horsepower, and those who race.. what can the transmission be expected to handle? Alls Ive heard is rumors, but even searching this forum I haven't found substantial information on transmission failures and causes. Also, Ive heard rumor that the '09+ transmission may be stronger, is there any truth to this? Any information would be greatly appreciated. Thanks!

 

Like with most stuff, it isn't as weak as some people say it is... But, 360whp and 240 torque is probably too much for it to handle well

 

Our transmissions won't last much with that power level at high rpms. What kills is is a mix of weak design and high temperatures.
You could be the first one to try an s2 tranny in a high output application though!

 

The 09/10 trans has fantastic synchros and does not suffer from the weak 3/4 shift fork that is notorious for bending. We have gone through two 04-08 trans per car per weekend with rental drivers who beat on them.

The 09/10 trans however has an input shaft that is about half the diameter of the 04-08.

I would head over to the RX7 club forums and post this. Those older school dudes will have a solution that will bolt right in. If I remember correctly the Turbo II trans is way more bulletproof. Somebody over there will know for certain.

You may know that tranny swaps can often require a different drive shaft length. This is NOT a big deal and its cheap. NOT a big deal. One of our crew guys runs my sequential box and had a new steel driveshaft made for only $90 Every large size city will at least have one driveshaft manufacturer. Again, it is quite common to have these made. Check it out.

 

Wasn't there a guy on here with a turbo or twin turbo rx8 that kept blowing axles and trannys? I recall him saying he was switching it over to an AT Triptronic because it was pretty rock solid tranny.

 

04-08 Aisin Tranny is made by Glass.

09+ Tranny is ok, but long term reliability is unknown at this time.

Like EricMeyer said, you better off use FD's tranny or Tranny from FC's Turbo II. or get HKS's tranny, its not cheap but it can hold tons of power. Turbo II tranny you can buy one for couple hundred bux.

 

Thanks for the info. I suppose I should have posted a bit of background information. I have been playing with Rx-7s for the past 10+ years. Owned many FCs, FD, and now and swapping a 20B into my '94 FD. I am already using a cobra 8.8 IRS rear end, so getting a driveshaft made is something Ill have to do anyway. Im aware that an FD tranny will handle the power no problem, but I was interested in the Rx8 unit for its better ability to handle the higher RPM shifting, as well as the tighter gear ratios. I dont , however, want to worry about breaking it all the time, so I guess Ill move on. Thanks again.

 

Like someone else said the reliability of the s2 tranny is kind of unknown with a higher HP car. Only somewhat recently was anyone even able to get the stock ecu tuned if they wanted to go turbo for more hp, so I doubt there are that many s2's making lots of hp out there.

It *might* be a good tranny but its hard to really say. You could be the test, lol.

 

just get a hold of richmond racing and have them build you a transmission.