Rotary_Knight

iTrader: (4)

Hello Everyone,

I just have a quick question. I have two transmissions on hand for my turbo motor that I'm about to install. I want to rebuild one of these transmissions. I have the JDM S5 trans and a USDM S4 trans. Which transmission would you run? This is a S5 motor and an S5 vehicle. I know the 5th gear is different on the S4 trans at 0.762 vs the S5's 0.719, and if I remember right a couple plugs may need rewiring, but that's no big deal. Just wanted peoples opinion if they have a preference. Thanks!

KompressorLOgic

iTrader: (6)

I prefer the s4 trans with the shorter 5th gear, makes passing on the highway super easy lol

Rotary_Knight

iTrader: (4)

Thanks for the feedback. That's also why I kind of like the idea of the S4 trans, and it doesn't have the silly shifter bushing at the bottom inside the shifter housing. When that thing goes bad, like it has in the S5 trans, it feels terrible and can be expensive/annoying to replace.

SpikeDerailed

iTrader: (7)

I own 2x USDM S5 transmissions and 1x JDM transmission, the JDM transmission def have a shorter 5th gear(64mph at 3k vs 71mph). Honestly i prefer the JDM shorter 5th gear.

Rotary_Knight

iTrader: (4)

Oh really? Awesome, it seems most people recommend the S5. I called a couple transmission shops in the area and they mentioned the S5 transmission has a special damper to help smooth the drivetrain. That combined with the info you gave me, it seems I'll be going the S5 route.

BLUE TII

iTrader: (9)

Yes, I went from USDM S4 TII with its short 0.762 5th to a JDM S4 trans with the even shorter 0.806 5th (same as most JDM S5 TII and JDM FD 5th as far as I know).

Pulled in 5th like a ****. Top speed dropped from 180mph to 170mph, but man you get there fast.

65mph is 3,000rpm with stock 4.10 rear and the 0.806 5th.

DC5Daniel

iTrader: (10)

I could have sworn I've read JDM S5 was taller than the JDM S4. Unless I'm misinterpreting your response, sounds like you say they are the same.

Rotary_Knight

iTrader: (4)

Well, it would make sense that the JDM transmissions have a shorter fifth gear since the speed limits are usually slower than most roads in the US. It would be nice if we could reference a JDM version of the factory service manual to confirm.

Rotary_Knight

iTrader: (4)

Hah! With some google translate help I was able to find a japanese site that shows the fifth gear in the JDM S5 transmission is much shorter at 0.806. I couldn't find the S4 spec's on that site though.

??? ????RX-7 [GT-R] FC3S? 1.4L/205PS FR/5MT ????? | greeco channel

KompressorLOgic

iTrader: (6)

My usdm s4 trans is on its last leg. I have an s5 trans I was gonna throw in. Hopefully it's a jdm one I want to keep a short 5th

driftxsequence

iTrader: (8)

LRB Speed offers a drop in delrin replacement bushing that makes it like brand new

Unfortunately they arent available to order at the moment, but it was $15 or less

Rotary_Knight

iTrader: (4)

Hey thanks for the tip. I ordered one some time last year, but I can't remember from who. I ordered it on ebay. It may have been them lol. Just haven't installed it as I figure I will after the trans is rebuilt.

devin122

Use which ever one you want. The internals are almost the same. IF you are rebuilding i would maybe start with the S5 since, IIRC they made some small revisions to the synchronizers (presumably to make them better). As for the 5th gear ratio, its not really an issue. On the counter shaft 5th gear is pressed on (opposed to all the other gears which are part of the shaft). This means you can swap them between any transmissions. Pretty you can also swap in 5th from simillar vintage B-series or MPV transmission, maybe the miata too.

misterstyx69

iTrader: (142)

Unless you got a real sensitive butt dyno..you'll never even notice any difference between the 2..so just shove one of them in and drive the car..lol!

DC5Daniel

iTrader: (10)

I disagree, it's very noticeable on the highway. Others in previous threads seem to agree.

Maybe all that Canuck maple syrup slowing you down?

valley

iTrader: (1)

Use whichever transmission is:
a) in better shape
b) has the tail housing required for your mount
c) has the better 5th gear (remember, you can downshift and a higher 5th means slightly less premium fuel to buy)

Rotary_Knight

iTrader: (4)

I've got quite the sensitive tooshy. lol

In all seriousness, I was looking into it in case there were any preferences to better reliability/durability between the two. The shorter fifth gear is just a bonus that I actually like it. This is not a daily driver, not concerned about gas mileage. I'll be sending out the S5 to get rebuilt next week.

misterstyx69

iTrader: (142)

I hope that your GF will treat your tushy with the best of care..heh,heh...if not I can send you out a belt sander..hahhaaa!

I guess I don't see the Benefits of swapping just because of a couple hundred rpm..when all I wanna do is get out and drive the car and do that without having to switch out every conceivable "questionable part" that pops up.
.my old school thinking says don't fix what isn't broke and enjoy the **** out of it until you break it!..

*(and if it breaks..take it out..and have Pancakes....WITH MAPLE SYRUP...mwuahahahaa!..DC5..leggo my EGGO!)

Rotary_Knight

iTrader: (4)

She treats me right, puts a little coco butter in there. lol

Naw, the decided factor was durability/reliability. I called a few mazda shops in the area to get their experience, and they recommend the S5 because it has some sort of harmonic damper inside that smooths out the drivetrain. Almost all the synchros in the transmission are done, except 4th to 5th, but that don't do me much good lol.