"The only real solution that seems to give you more breathing room is"......

a T56.

beats band-aiding a trans that was designed for 217 foot pounds of flywheel torque in a car that weighs (w driver) 300 pounds less. then you can run the real turbo that you want...

there are plenty of F body 2.66 first gear T56s in boneyards, just like what i have run since 2012... and they shift fine at 9 and deliver way better ratios.

combine w a Mcleod RST double disc that will hold any motor yet feathers on takeup and is easy on the left leg.

a perfect project for your new garage..

You left out a few details maybe ...

Like a drive shaft and a custom.clutch and tranny mount and diff mount and custom shifter so it comes out someplace close to stock.......

Not as easy as it sounds...

I still have a good FD gearbox that I will explode first before spending all that money. It looks like I will have to replace my tires and don't think I will stay with the 15" drag radials. They are just too sticky, wear too quick, and can't be driven on damp roads (let alone rain).... They are great for traction, but the drivetrain is stressed to the max with these.

https://cimg8.ibsrv.net/gimg/www.rx8...7662d727e7.jpg

I am looking at Potenza RE-71Rs in 245/40/18 (25.7" diameter) or 245/45/18 (26.7" diameter) for the stock rx8 wheels for the rear.... Maybe even 235/45/18 (26.3" diameter). It looks like those would be a compromise between 15" DRs and low profile street tires. I like the tall diameter to give it a bit more sidewall and give me longer gears.

I am slowly getting my garage in order and will likely be pulling the tranny next weekend. Loving all the space in my new garage. 25' depth should be standard.

https://cimg0.ibsrv.net/gimg/www.rx8...9e164fd7cc.jpg

:yelrotflm

Nice garage space. :icon_tup:

I’m using the Conti extreme contacts in stock format (225/45/18) with stock wheels. I think with the power you put down burnouts would be easy without stressing the clutch or drivetrain components too much. Very sticky though when cornering at high speeds.

by the way awesome garage and nice mk4. Congrats on the new place!

Go 245/40r18 re71r you wont regret it

i have 265/35r18 re71r on all 4 corners and i like them alot, bought these thinking i would do some lapping with it but never managed to yet. Maybe ill try michelin ps4s next

Pulled the transmission down Saturday morning. Swapped the bell-housing and tail section on Sunday morning. Ran through the gears and twisted the main shaft and everything seems normal. Should have it back up and running by next weekend.

I will take apart the old trans when I get this project done. When I picked up the old gearbox I could hear metal cascading from one side to another.... the magnetic drain plug was caked in debris. Fluid wasn't too bad.

Clutch was operating normally so I will just leave it for now. It only has about 500 miles on it since I swapped one of the sintered iron discs for the high performance organic (to soften up the ride). Once I verify that the transmission operates correctly, I will be ordering the 245/45/18 (26.7" OD) RE-71 tires to mount on the stock wheels.

Plan is to ramp up the boost in a more linear fashion to keep full boost from hitting between 4000-5000 RPMs. This is strictly to keep the trans alive longer. Keep boost to 15 psi between 4-5, 20 psi between 5 and 6, then all of it above 6.... something like that.




https://cimg5.ibsrv.net/gimg/www.rx8...20b8fc9105.jpg

New (old) transmission on. Runs through gears 1 through 5 with ease. No weird noises so far.

However, getting in and out of reverse takes a lot of force. Not sure exactly whats going on there. What can you expect from a 25 year old gearbox that was bought from a junkyard???

Edit: Looks like from what I read that if you overtightened the reverse light switch (which I did to get the wires not to rub on the transmission tunnel) it will make getting into reverse difficult. I maybe just have to loosen it a bit to make reverse easier to get in and out of.

Anyways pulled the window off of the old gearbox and not too much of a surprise.... I'm shocked how little meat there is on each gear....

Update: shimmed the reverse switch and car easily goes into reverse now.. Shifter is feeling sloppy as hell now, the bushing disintegrated when I pulled it apart. I need to find which bushing goes in the bottom of the shifter...

https://cimg5.ibsrv.net/gimg/www.rx8...1b97607b92.jpg

Dang :Eyecrazy: .That’s what torque does to these transmissions I guess lol. I feel like my 4th gear looks like that right now.

:shocking::shocking::shocking:

Update - Looks like the 5 speed rx8 transmission and FD transmission share the same shifter so I ordered a new shifter bushing for an FD and hopefully it will fit the rx8 5 speed tranny. The slop right now is unreal.

Also, 245/45/18 R-Compound RE-71 have been ordered. Can't wait to be able to take a corner at more than 15 mph (MT drag radials)...... Car will look completely stock now with stock rx8 wheels, exhaust is only giveaway that you may get gapped.

:icon_tup: Nice. Same look I'm trying to achieve. :ylsuper:

meh, have done that to 2nd gear on 4 or 5 6-spd boxes with NA Renesis :lol:

a better solution IMO is a PAR straight-cut gearset, but going to set you back about $5300 + install

I looked into those for a minute, but decided to go with a 370z trans instead. Much cheaper, and easy to replace. i need to get rid of my RX8 5speed.

Well since that kit was designed for fitment in the FD3 and not the RX8 chassis, whether it’s cheaper after the final install remains to be seen. It also has a lot less capacity than the PAR gearset.

.

Either way, there is no way I would spend 5k+ on either swap when I can buy another 5 speed gearbox for $500. Even if I put in a stronger transmission, I would just be shifting the weak link to the rear end, axles, motor, etc.

It seems that going over 500 rwhp, the drive-train and motor costs are going up exponentially at this point. Definitely not worth 10k+ to get the car up to 600 rwhp+.

Plan is just to just get it up and running, turn the boost down in peak torque range and let it eat up top. With the r-compound 18's on it would likely not hold the power anyone once the turbo hits, so this solves two issues.

If anyone wants to buy this car for pennies on the dollar don't be afraid to make an offer..... :)

Yeah, the Monsterbox 4-rotor FD3 is putting 1000 hp/600 lb-ft through a 5-spd w/PAR gearset, but it has dog gears rather than synchros. They have a synchro set too. It’s held up so far, but that’s definitely pushing it. I don’t really feel like your power level is going to be a driveshaft, axle, or diff issue, except the LSD is not that good even for the NA power level imo. I knew you wouldn’t want to spend that, just info for the readers.

I also saw you make that offer before, very tempting.
.

Given everything you've put into this car, I suspect you will regret letting it go. If not, my daughter's piggy bank has a few thousand pennies in it....:yelrotflm

New tires on back 245/45/18 - 26.7" OD - RE-71R. Fill up the wheelwell nicely and look completely factory on first glance.

https://cimg7.ibsrv.net/gimg/www.rx8...b91890751a.jpg

https://cimg9.ibsrv.net/gimg/www.rx8...d786438af9.jpg

Those should spin up well 😏

Just took the car out and not used to the wheels spin. Maybe need to break these in a bit. Last tires only got like 1500 miles. Maybe these will get 5,000?? It is nice being able to take a corner at more than 10 mph.

Limited boost to 16 psi until 5500 RPMs. Hitting 20 psi by 6,000 RPMs. Will go for 24 psi by 6,500 RPMs and keep it there to redline. IT will be fun to play with boost by gear and RPM to give just enough horsepower to keep the new tires planted....

Tranny seems to be okay. Turned it down a but on the first pull so I don't break something on day 1.

Congrats on getting the tranny in and rolling again!

New pull last night on the new trans with longer 3rd gear and large diameter tires. I still have to re-calibrate the speed sensor and gear detection stuff to account for the change.

I'm going add in the boost with RPM like a centrifugal supercharger to keep the torque from hitting all at once when the engine isn't wound up. You can see the dull purple line is the wastegate duty cycle that increases with RPM. spun top of first gear, start of second gear felt lazy, 3rd felt good. Also, I think I will stop doing the lugging 3rd gear pulls as this tends to load up the turbo at the low RPMs and that's what killed the tranny. Going to run through the gears more like a simulated race.

12 psi first gear, 18 psi 2nd gear, 22 psi third gear but let out early should have been near 24 psi at the top.

Will add a few more percent of fuel between 5000-6000 RPMs.

Eventually like to get some more ethanol and ramp the boost up higher in the 6000+ area. Raining tonight :banghead:

Also, I did the calculation that Team mentioned above.

Previous - With 26.2" OD tires, 1.484 3rd gear ratio (rx8 5 speed), and 8,200 RPMs speed should be 97 mph, which makes sense because I ran 97 mph in the 1/8th mile and I was shifting right at the markers.

Current - With 26.7" OD tires, 1.391 3rd gear ratio (FD gearbox), and 8,200 RPMs speed should be 105.4 mph....

This is going to be some real long gears, which should make the car easier to drive.

https://cimg1.ibsrv.net/gimg/www.rx8...57c2b0fc59.jpg






https://cimg7.ibsrv.net/gimg/www.rx8...32ba036610.jpg