Is there a difference between the JDM Turbo transmission and the US version? And is there a difference between s4 and s5 turbo transmission?

 

S4 and S5 Jspec transmissions have a 0.806 5th gear, and the 5th gear switch is absent.

S4 and S5 transmissions in general have different mounting positions for the crossmembers, and the US versions have 5th gear ratios of 0.762 (S4) and 0.719 (S5).

 

Oh cool. i only ask cause there is a JDM transmission in my area for a few hundred with no grinds. Mine grinds and leaks. So the s4 trans wont work for the s5 right? Also what is the 5th gear switch and what does it do?

 

If the S4 transmission has the matching crossmember, it will bolt right into an S5.

The 5th gear switch is used by the ECU to trigger the split air solenoid, which directs air to the main cat. It also prevents the shift up light from coming on in 5th gear. To make it easy, you can just transfer your existing US 5th gear / reverse switch to the new transmission. They go in the same location.

 

Will anything be negatively affected if i never put the switch in? Just curious.

 

The shift up light will come on in 5th gear, but that's it. Smog tests aren't performed in 5th gear, so there's no emissions testing consequence.

 

Bringing this one back.

I've got a S5 JDM engine and tranny swapped into my vert. I didn't do the swap, I paid a shop to do it. Because of that I'm a little unsure about the details of this...but here's my situation.

My reverse lights never worked after the swap, which never really bothered me much. But now that I'm rebuilding the engine I'd like to fix this. If I'm understanding this correctly what I need is to get a USDM S5 switch for the transmission and that will plug into my N/A harness?

Just read another thread on similar topic. From that one I can simply plug my 2 plug harness into the transmission's matching prong and that will have my reverse lights working. I don't really need to worry about the 5th gear switch.

 

You do not need the 5th gear switch to get it to work. Just match up the reverse switch to your harness. If you changed series the plug may be different and you will have to install a new plug. For a long time I just soldered them together but it got annoying to have to redo it anytime I took the trans out.

 

off topic sorry

so your telling me that the split air valve is optional for our cars to be carb compliant?

 

I'm going to dig all my parts out of storage to get ready to finish my rebuild. Transmission has been in storage long enough that I don't remember what is on the transmission...if anything. I've got most of the harnesses out of the car. While everything is out I'll simply solder whats needed to create a harness for the reverse lights.

No, what he is saying is that so far as the transmissions 5th gear switch is concerned it won't affect emissions testing because they do not test your car in 5th gear.

 

You mean swap out the 5th gears not just the switch?

 

The Split Air Solenoid is only engaged in fifth gear.

No emissions test is done in fifth gear.

One plus one equals two.....more or less.

 

Plug in the 2 wires for the reverse switch, and forget about the 5th gear switch wires. That's how I did it on my car, and as I mentioned before the only noticeable consequence is the shift up light coming on in 5th gear.

You could fail a visual smog test if you leave the solenoid unplugged or remove it in an obvious way, but it has nothing to do with an idle or 15/25 mph test.

What? No, the 5th gear/reverse switch is a 4-prong switch on US cars. The JDM version is just a reverse switch with 2 prongs.

 

^ oh got it. Thanks!

 

Understood. I have yet to look over my transmission for the pins...I'm going on the assumption that it wasn't removed or broke off the transmission while in the junkyard or during shipping.

I don't have to worry about the shift up light. I have a S5.

 

You should get an S4 cluster/ECU/wiring so you can have one. It's SO useful to have the light come on at 2500-3000 RPM. Clearly an optimal shift point. Especially when it wants me to put it into 6th gear.

 

Hehe..well the 2500-3000 shift light might be useful during engine break in?? I don't know...I'm looking for the silver lining here....