Japanese Transmission in American SVX

[Nomake Wan]

Originally Posted by 97 SVX

Is it correct that there is a diffferance in the JDM's And USDM (canada) trans.

If that really is a Japanese transmission, then yes. There is a major difference between it and the US transmission. As in the thread in the link I gave a few posts up, the Japanese transmission is VTD whereas the USDM transmission is not. This means that US transmissions send power to the front wheels constantly and use an electronically-controlled transfer clutch to send power to the rear, up to 50/50.

The Japanese VTD system, on the other hand, is set up to send power constantly to the rear, and uses a limited-slip differential to transfer power forward, up to 50/50. Normally, the car's power distribution is 35% front 65% rear. Big difference. Plus, the final gear ratio on the US trans is 3.54 and the Japanese one is 3.7 (which is why you have to change the rear differential).

[subarufamily]

svxmotorsports.com is a good place to start they helped me out alot with stuff for my svx they have vehicle specific parts and places to buy and NOT to buy

[Nomake Wan]

Originally Posted by subarufamily

svxmotorsports.com is a good place to start they helped me out alot with stuff for my svx they have vehicle specific parts and places to buy and NOT to buy

Since that site does not exist... are you referring to Dayle's site?

http://svx-motorsport-accessories.stores.yahoo.net/

[subaru-jin]

I was able to get the mounts I need from a Subaru dealer in Sydney. I just looked on the global subaru website, selected Australia, searched for dealers in Sydney and then called them up. They shipped them out yesterday via air mail. Hopefully they'll get here by the end of next week. I'm really looking forward to getting my SVX fixed so I can really drive it.

Also, I emailed the guy that got the transmission for the previous owner. He told me that he didn't change out the TCU.

Jim

[subaru-jin]

So, finally I got the parts! Well, I had to wait another week for the shop to get to it. They got the mounts in today and... It still makes noise, but not quite as much... They say it's coming from the transfer case. At first they told me that the transfer clutch was burnt and they needed to rebuild the entire transmission. The reason it went out, they said, was that the front and rear differential ratios are different in the car. Whoever put the JDM tranny in screwed up. I told him that the JDM tranny has a differential instead of a transfer clutch. So, he's going to pull the transfer case on monday and look.

Is it possible that the front and rear diff ratios are supposed to be different because of a ratio other than 1:1 in the center diff?

Is it possible that the entire transmission doesn't need to be rebuilt and just the center diff? Hopefully saving me a few $1,000s?

Please help. I'm so frustrated with this car. It's been screwed up ever since I bought it.

Thanks,
Jim

[Nomake Wan]

Originally Posted by subaru-jin

At first they told me that the transfer clutch was burnt and they needed to rebuild the entire transmission. The reason it went out, they said, was that the front and rear differential ratios are different in the car. Whoever put the JDM tranny in screwed up. I told him that the JDM tranny has a differential instead of a transfer clutch. So, he's going to pull the transfer case on monday and look.

Is it possible that the front and rear diff ratios are supposed to be different because of a ratio other than 1:1 in the center diff?

Is it possible that the entire transmission doesn't need to be rebuilt and just the center diff? Hopefully saving me a few $1,000s?

That's very strange that they'd suggest a transfer clutch. From what I remember, Australia and New Zealand both got the JDM models, including JDM VTD-4WD transmission. They did not get the ACT-4 transmission we in the US did. So now that I think about it... was it really a JDM "swap?"

That said, it may still be a transfer clutch mechanism. I'm a little fuzzy on the detail for it; the diagram I read simply stated that power is transferred forward via a limited-slip differential. How the initial power split occurs, I don't know. It shouldn't be an electronic device, though, because our electronic transfer clutch is there due to having to transfer power AWAY from the FRONT. Whereas the Japanese transmission always powers the REAR and transfers power FORWARD. Totally opposite.

The final ratio for the JDM transmission is 3.70. The rear VLSD ratio is 3.70 as well. So I can only guess that the front differential is also 3.70. No clue what the ratio on the transfer LSD is, but if I had to guess they probably used the same ratio...

[subaru-jin]

Originally Posted by Nomake Wan

That's very strange that they'd suggest a transfer clutch. From what I remember, Australia and New Zealand both got the JDM models, including JDM VTD-4WD transmission. They did not get the ACT-4 transmission we in the US did. So now that I think about it... was it really a JDM "swap?"

I'm actually in the US. The car is US. The transmission is JDM. I ordered the replacement mounts from a dealer in Australia.

Originally Posted by Nomake Wan

That said, it may still be a transfer clutch mechanism. I'm a little fuzzy on the detail for it; the diagram I read simply stated that power is transferred forward via a limited-slip differential. How the initial power split occurs, I don't know. It shouldn't be an electronic device, though, because our electronic transfer clutch is there due to having to transfer power AWAY from the FRONT. Whereas the Japanese transmission always powers the REAR and transfers power FORWARD. Totally opposite.

Do you think there's a problem using a US TCU with the JDM TCU? Someone said that they thought they were "plug-and-play" and there shouldn't be a problem. Does that mean that the TCU "knows" which transmission it's connected to? And does it's thing accordingly?

Thanks!
-Jim

[TomsSVX]

Originally Posted by subaru-jin

I'm actually in the US. The car is US. The transmission is JDM. I ordered the replacement mounts from a dealer in Australia.



Do you think there's a problem using a US TCU with the JDM TCU? Someone said that they thought they were "plug-and-play" and there shouldn't be a problem. Does that mean that the TCU "knows" which transmission it's connected to? And does it's thing accordingly?

Thanks!
-Jim

No. the TCU will function according to its programming... If its programed to run a USDM trans... It will only work properly with a trans that needs/has the same programming. you would need the JDM TCU to make it function and that is IF and only IF it is plug and play

Tom

[subaru-jin]

Originally Posted by TomsSVX

No. the TCU will function according to its programming... If its programed to run a USDM trans... It will only work properly with a trans that needs/has the same programming. you would need the JDM TCU to make it function and that is IF and only IF it is plug and play

Tom

So, what would happen if you used a JDM TCU with a USDM transmission? I think that's what is in my car, anyway. Can it damage the transmission?

And what exactly does it mean for a TCU to be "plug and play"?

Man, maybe I should have sent the car off for a 5spd. This is a pain in the butt...

Jim

[Nomake Wan]

Plug-And-Play means it just plugs in and works.

But I didn't know you were using a US TCU! That's no good! The US TCU isn't programmed to operate a JDM transmission! Get a Japanese TCU and you should be okay... hopefully...

I don't know if it would do damage, but it won't operate properly. That much I know.

P.S. When you get that new TCU, ground pin A4.

[TomsSVX]

The JDM TCU differs in how it actuates the AWD. that is the key difference... The trans should match the TCU no matter what

Tom

[subaru-jin]

My mechanic took the transfer housing off my transmission today and found that it has a clutch pack and not a differential. It must be a JDM transmission though since the JDM mounts work and the USDM mount doesn't. Is there a technical discussion somewhere on how the clutch packs work?

[Nomake Wan]

Wow, the site that was hosting the technical explanation for the VTD transmission reconfigured and now I can't find it.

Oh, Archive.org has it still though (but without pictures, awwwww). And reading it again, it does say "...torque distribution is controlled by an electronically-controlled limited-slip multiple-disc clutch pack." Um... is there such a thing? Can a clutch pack be limited-slip?

EDIT: Archive.org link: http://web.archive.org/web/200304082...vtd_pada03.htm

[subaru-jin]

yeah, I saw where you mentioned that page before and I couldn't read it (I can't read Japanese). Just now, I had translate it... WOW...

So, I guess it has a stack of clutch discs (Like in a motorcycle?). Does it basically feather the clutch using an electronic servo to vary the torque distribution? It seems like the clutch plates would wear out from normal operation over time. Is that true?

Thanks for all the help!

-Jim

[Nomake Wan]

Sadly, all I can do is translate what's there... when it comes right down to the mechanicals themselves, I have to hand it off to someone who knows more about these transmissions than I do...