I've got a 93 FD with extensive engine work done by Rotary Performance. Love this car and their work. Can't recommend them highly enough! But I now find myself on the east coast and will need to replace my transmission in the forseeable future. RP told me that I've maxes out what pump gas can do on my car. When I turn on the profec b im pushing 440 horse under the hood. It's a street car right now but I may get into putting it on the track. Of course it had developed 5th hear issues and can "rattle" in some others.y The tranny has been rebuilt once already so I'd day it's on its last legs.

My question is what transmission options are there? I've seen an after market one for $10k. But I don't know if there are others. Or is getting a new tranny just the best option? Thanks!

 

https://www.rx7club.com/showthread.p...t=transmission


read up on this
the whole thread, its being discussed here.

 

One other option is just getting a good used JDM transmission. They go for $350-400 or so, you can buy a LOT of those for the cost of a big time transmission. Also, low mileage makes a HUGE difference, a nice low mileage transmission is a totally different animal from a 100k+ transmission.

If nothing else, get one, put it in, and get the car back on the road while you research other options.

Dale

 

Is the JDM six speed any good? I keep seeing these for sale.

 

You say it was rebuilt before. Who rebuilt it and when? Another thing about this transmissions I have noticed, even on rebuilt ones, is that in high power applications they do like semi-frequent gear oil changes. Redline MT-90 is known to work well.

Personally I don't think it would be worth it for you to try and swap in another kind of transmission. Banzai Racing is running a stock transmission on their 20B FD.

 

The 5th gear / synchro issue is not caused by elevated power output. So at 440hp I would not say your transmission has failed any differently than it would on a stock motor. Other known weaknesses are worn bearings (only good for 50k IME), rough shifting into 2nd gear (just a design issue) and in high shock / high power applications you can shred the teeth off of 3rd gear.

I would replace the transmission or consider getting it rebuilt. If you only need work on 5th gear and the transmission has lower mileage I'd rebuild just that stuff. If it needs a full rebuild, the price on low mileage JDM transmissions make the rebuilding somewhat obsolete unless there is something special you'd like done on the internals like shot peening or microfinishing. The used JDM transmissions are technically a risky proposition because they are used, but the general experience of everyone on the forum with them has been very good.

 

Pettit has theirs i would call them, it is essentially a rebuilt with a few tweak from them from what i understand. The price isn't bad either.

 

What about using a replacement gear set? http://www.osgiken.net/products/closeratiogear.html

 

The OS Giken is a good gearset but it costs as much as about 8 good used transmissions. Obviously reliability is important but IMHO until you've broken one or two stock gearsets it's not really justified. It also uses the stock bearings so if your transmission died of bearing death it won't help much.

I am however curious about the 3 speed OS Giken retrofit. By all accounts, these are the gears where ratio tweaks and extra strength would be very beneficial.

 

I ripped the teeth off of 3rd gear down at DGRR in 2010 after making many 500 rwhp highway pulls.... this on my original trans that had been rebuild three times, total of ~120k miles on the box.

I've since been running a JDM trans with good success, although I haven't repeatedly beat on it at those boost/power levels since. Sure, I'll make some 20-21 psi pulls, but I give the trans time to cool off.

I have the OS Giken setup waiting to be installed..... i had it for one track session but the shifter kept popping out of third gear around peak torque, so the trans had to come back out. PITA to be sure. Hoping this time the trans shop can get the clearances worked out. The owner has never steered me wrong through numerous diff/trans jobs for many FDs, this was the first hiccup we've ever had.

There's a lot more info on the OS gearbox in my build thread (ratios, speeds at redline etc) which is temporarily offline.

 

there is another option, just depends on how simple you want the solution to be. R154 box from mklll Supra is an option with far better ratios than stock, and not nearly the cost of the T56 or a new gearset (quaife, OS, etc).