Will the FD autodiff fit into the TII pumpkin? or will the 3.90 gears bolt onto the S4 tII diff? I have an 88 tII with jspec tran and want to bring the hiway rpm back down. This might be the best way to do it. Seems like plenty of FD auto guys do the auto to manual swap and there seems to be some of these always available.

thanks

 

um no
wrong-o

if you really wanna go ahead, but changing your rear gear will make EVERY gear slower

ideally what you need chaged is your 5th gear ratio . . .

which i'm sure is possible

but i dont know where to go for that

 

Yes, I have checked around on this board and got a resounding NO! from all the bigboys when asking about changing the 5th cog.

I know that it makes all the other gears steeper as well, but that is not as much of a concern; I have kinda gotten all that 1/4 mile racer attitude out of my blood by this time. I'm having quite alot of fun with my n/a vert. The TII with the 3.90 will be much quicker through the gears in every way than the vert.

But, even if yoiu don't think the ratio is a good idea, do you know if it will fit?

Thanks

Jack

 

No the 3.90 would be slower through the gears. the 390 had a higher top speed and slower accel. you want the 4.30 rear end out of the GTU.

the miata tranny gear swap might intrest you, do a search for it.

EDIT: woops my bad, i misread your post. lol yes the 390 would bring highway rpms down

 

in japan they made automatic t2's. You may be able to find one from a japanese junkyard if the FD pinion and ring don't fit.
I don't believe that they do, but I'm not positive and am somewhat often proven wrong, so keep asking

I had the same idea, better gas mileage! The 4.3's are looking nice though

miata tranny gears are close ratio, also think they only fit in n/a trannies. I would think a FD 5th gear would work, but seems as if you already got a no.

 

someone please answer this (someone who is sure of their answer)
cuz i want a 3.90 gear in my TII diff, and so far i'm hearing i cant.

 

I belive you can use the 3.90 ring and pinion from the FD on a tII diff. Try searching, there was a thread about this a couple of months ago it had to do with items you can use from the fd on our cars.

Id rather go 4.30 but its your car and you know why you want 3.90 gears.

JP

 

93.5% you cant, the FD pinion is shorter then the FC one, so unless you want to cut and weld the pinion,...


The actualy torsen diff, however will bolt right in.

 

FD ring and pinion are not interchangable (at least the pinion isn't). If you have a S4 TII with S4 tranny, you could get a S5 tranny instead and go from a .762 5th gear to a .719 5th for better highway mileage.

~Mike.............