I was wondering which out of the two would be the best desicion. I really dont want to modify the floor or cut tryign to put a different type of transmission to hook up to the 20B. But then again i also need a transmission that is going to hold at least 950hp with out trying to go out on me in a couple months. And no this is not a drag car, it will be a high powered street car. any suggestions.

 

there is lots of info on transmission options on this board so i suggest you search.

the fd trans works fine around the 550 rwhp level if not abused. it will not work at levels above 550 especially for drag racing.

you are looking at the correct trans option in the T56. the getrag supra trans is really nice but it has a 1 to 1 6th gear so you'd need to find (non-exsitant) 3.13 rear gears to make it work correctly. it would work if you swapped the cobra rear.... again a search will locate the info.

at some point i will swap to the t-56. it requires a custom input shaft (Liberty Gear), a 4 inch rearward spacer to clear the starter etc....

do not neglect the trans if you plan to be making big hp.

howard coleman

 

The Supra trans has a 1:1 5th gear, not 4th. Sixth gear in the Supra trans is .79 and that is slightly taller than the stock fd trans iirc but you may want to verify that. The stock gearing in the Supra trans is far better than the T-56. You get a close ratio 5-speed with a granny 1st essentially.

The T-56 on the other hand has two overdrive gears, 5th and 6th, the latter of which is useless except mileage concerns on the freeway. Top speed would be reached in 5th gear which is still very tall. Fourth gear is the standard 1:1. You get a close ratio 4-speed with two overdrive gears in the stock T-56.

The T-56 is cheaper and easily available with more aftermarket support.
All else equal, the Supra trans will more than likely get around a road course quicker and out accelerate the T-56 equipped car. The T-56 though will have a higher top speed.

Also, as Howard mentioned, there are Cobra 8.8 diff/gearing options available for the FD to mix things up even more.

Good luck.

 

thanks dave, i was typing in advance of thinking.

i believe there are two "V160 and V161" versions of the getrag box. they differ a bit on gearing. the numbers i have on one of the boxes...

........... FD..................Getrag

1st........ 3.483.........3.83
2nd....... 2.015........2.36
3rd........ 1.391........1.69
4th.........1................1.31
5th......... .719...........1
6th.......... NA............. .79

of course there are a couple of other 5th gear ratios. i run the .82 from a mazda pickup.

one of the reasons i am interested in the T56 is i want to run 200 mph at the texas standing mile and the higher ratios in the T56 work well. there are lots of ratios avail for the T56... the new (09) T56 for the GT500 for example.

 

Here is one thread on a completed T56 conversion:
https://www.rx7club.com/20b-forum-95/tranny-update-655772/

There is another in this section somewhere with lots of gear info if you search for it.

 

This is a nice thread as it cuts to the chase instead of reading a thread a mile long. I am going Friday to pick up my trans that Liberty just built for me. It is stock with the gears heat stressed relieved and cryo treated. I'm making 560-600whp @ ~420 ft-lbs. We'll see if this holds up.....I'll post results.....

 

So vincentrx7 let me know how the transmission works out for you.

My whole thing is that I have an RX-8 and really don't to cut up the floor when i can u an FD transmission and make it fit like the stock on. My other is issue is how heavy is the T-56? Because i already know by adding a 20B to my car is adding more weight to the car. ??

 

your ******* looney