Hi,

I put a Jdm driveline (ex. Diff) in my 87 tii over the summer and reflecting on it now it seems the the overdrive is much lower when comparing it to my usdm s4 trans. Can I get a conformation on this and possibly a ratio?

Thanks

 

The japanese transmissions do have a taller shorter 5th gear, something like .83:1 vs the .72:1(s5 tii) or .76:1(s4 tii) of the usdm.

 

If you search with my screen name as reference, you'll find a long conversation in this regard. In short, S4 TII and JSpec S5 TII tranny's have essentially the same 5th gear ration. ASpec S5 Tranny's have the taller 5th gear ration, perhaps because they had more HP. Regardless, that is exactly why I went with S5 TII trannys in my DD TurboVerts.

 

taller shorter...

is an oxymoron, by that ratio if the jdm had a .83:1 it would be the tallest not the shortest. the trans i have in my car (jdm s5) has a much shorter 5th (overdrive) gear. .72 is the shortest while .83 is the highest when speaking in terms of OD gears. they mean that for every one revolution of the engine you multiply it by 1.xx ratio for the overdrive. so a .83 is really almost a 2x output speed gear.

 

what your saying is that there should be no change in OD gears s4 USDM vs s5 JDM?

 

The brochures in the standard specs sticky are fixed, so you'll find the USDM ratios in there: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/specifications-what-did-2nd-generation-rx-7-come-w-options-standard-features-642372/

S4 USDM TII: 0.762:1
S5 USDM TII: 0.719:1
S4 & S5 JDM: 0.806:1

I have an S5 JDM transmission in my car, which puts the engine at 3600 RPM @ 80 mph w/ a 4.1 rear. If I had the USDM version with the 0.719:1 gear, it would be at 3200 RPM @ 80 mph.

Speed calculator: http://www.catherineandken.co.uk/sti/tyres.html

Thread Hozzman mentioned: https://www.rx7club.com/showthread.p...ight=jspec+5th

 

so the jdm is lower, quite a bit lower...

 

^ Ah, how is he going to learn to fish if you just serve the fish up?

 

I was feeling generous. It happens every once in a while.

 

or was the fisherman feeling lazy and would rather play the fool to play someone else the fool

 

^Dude, don't go there. You're just exposing yourself.

By the way, the measure of taller vs. shorter is the gap between 1:1 and final (some would say over) drive. Thus, JSpec final gear ratio is shorter than ASpec final gear ratio. There, you're now more prepared to be on Jeopardy.

Merry Christmas.

 

i had that backwords when i explained it earlier

i fully understand the way a ratio is implemented on a lever (IE gear in this case)

 

Well my friend, be a good guy and if someone asks about twisting a nut onto a bolt, please be careful to not explain "Righty loosey, Lefty Tighty".

Drive safe.

 

i've told myself that on accident before lol, comes with having dyslexia and dyscalculia