Muskiefshr Posted November 4, 2021 Share Posted November 4, 2021 Okay folks, this is my first post here. I’m pretty familiar with 2nd gen outback’s but automatic transmissions are not something I’m super familiar with. Here’s what I’m trying to do…I have a 2003 OB 3.0 H6 non-VDC car that has 68k miles on it. Even with the low miles, the transmission has a violent 4-3 bang shift, bad enough it will chirp the tires. As I live in Utah, this isn’t something I want to live with in the mountains. I did a service and added trans-medic but had no difference on the performance. I found a 2001 OB 3.0 H6 VDC car with 165k miles that unfortunately had an interior fire. I got the car super cheap and it ran and drove well and had a lot of good parts on it. So here is my questions…is it possible to swap the center differentials out? What activates the VDC on that transmission? I took the tail housings off both transmissions and they are quite different. It appears that there are parts to each different system pressed onto the transmission main shaft.What do you guys think I should do here? I don’t want any weird flashing lights on the dash…just a working trans and AWD. Link to comment Share on other sites More sharing options...
Numbchux Posted November 4, 2021 Share Posted November 4, 2021 This thread mentions putting a VTD center diff housing on a 2006 MPT transmission. Not really specific on the details, but one picture of the different parts, and some parts lists. https://www.subaruforester.org/threads/2006-mpt-to-vtd-conversion.37441/ I don't think I'd bother. '01-'03 LL Beans are not rare. Just get the correct transmission and swap it in. Link to comment Share on other sites More sharing options...
Muskiefshr Posted November 4, 2021 Author Share Posted November 4, 2021 So what would happen if I installed the VDC trans with the VDC center diff in my non-VDC car? It appears the the speed sensor and reluctance wheel are exactly the same on both transmissions. Not sure what the sensor on the center diff is, but it also looks the same. And as far as I can tell, all the other trans electronics are the same. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 5, 2021 Share Posted November 5, 2021 Is the downshift flare only happening at highway speeds? Try a battery disconnect reset and then road test. If better, yeah, they all do that(seriously) Link to comment Share on other sites More sharing options...
Muskiefshr Posted November 5, 2021 Author Share Posted November 5, 2021 (edited) The downshift flare was worst at around 40-50mph. It basically slips on the 4-3 downshift. I can see the revs go up higher for about a second or two then actually go down when it bangs into third. It would also take around 5-7seconds to actually go into gear when shifting from park into drive or reverse. I did the battery disconnect and replaced the TPS sensor with a brand new OEM Subaru one. Did not help. I believe that there is something either going on with the pump in the trans or the torque converter. I know the 6-cylinder 4EAT is a bit of a sloppy shifter, but this one definitely has some bigger issues. I’ve had a couple of these 3.0 OB’s and while none shifted great, none of them shifted this bad either. Edited November 5, 2021 by Muskiefshr Link to comment Share on other sites More sharing options...
idosubaru Posted November 5, 2021 Share Posted November 5, 2021 Can you swap those parts on the main shaft? Maybe check part numbers - if the main shafts are the same part number then the guts may be interchangeable. If the trans case the rear extension housing bolts to is the same part number then the extension housing case should bolt right up. If course this logic doesn’t work the other way (if they’re different part numbers they still may interchange, very common for that to happen). Its been awhile but I thought all JDM H6s have VTD even if they’re not VDC. If that’s the case then what you’re ideally trying to do should be possible by removing everything possible out of the extension housing and swapping. I’m pretty sure us VDC people buy JDM non VDC trans and bolt them right up. Pretty sure I’ve done that. That doesn’t guarantee the JDM trans are the same as US but I’d be surprised if Subaru made a different trans (VTD non VDC H6) just for JDM. 1 Link to comment Share on other sites More sharing options...
Muskiefshr Posted November 5, 2021 Author Share Posted November 5, 2021 5 minutes ago, idosubaru said: Can you swap those parts on the main shaft? Maybe check part numbers - if the main shafts are the same part number then the guts may be interchangeable. If the trans case the rear extension housing bolts to is the same part number then the extension housing case should bolt right up. If course this logic doesn’t work the other way (if they’re different part numbers they still may interchange, very common for that to happen). Its been awhile but I thought all JDM H6s have VTD even if they’re not VDC. If that’s the case then what you’re ideally trying to do should be possible by removing everything possible out of the extension housing and swapping. I’m pretty sure us VDC people buy JDM non VDC trans and bolt them right up. Pretty sure I’ve done that. That doesn’t guarantee the JDM trans are the same as US but I’d be surprised if Subaru made a different trans (VTD non VDC H6) just for JDM. So I did a little more work in the shop last night on the transmissions. The extension housings are different but have the same bolt pattern on both transmissions. The main shaft coming out of the trans is actually a short, splined stub shaft that pops out with some gentle prying. I can definitely swap the entire center differentials. However, I’m curious if there would be an advantage to keeping the VDC center diff. Link to comment Share on other sites More sharing options...
Numbchux Posted November 5, 2021 Share Posted November 5, 2021 (edited) The VTD is a far superior AWD system, and while they use the same clutches to actuate it as MPT, when they are actuated is different. The post I linked is a guy that used the VTD mechanicals with an MTD system. He talks about using the FWD fuse to change how it operates. I think he's likely relying on the mechanical function of the diff, and the electronic LSD function is not likely working (like using a DCCD center diff without a controller). But I'm not sure exactly. Edited November 5, 2021 by Numbchux Link to comment Share on other sites More sharing options...
idosubaru Posted November 5, 2021 Share Posted November 5, 2021 (edited) 3 hours ago, Numbchux said: The VTD is a far superior AWD system, and while they use the same clutches to actuate it as MPT, when they are actuated is different. The post I linked is a guy that used the VTD mechanicals with an MTD system. He talks about using the FWD fuse to change how it operates. I think he's likely relying on the mechanical function of the diff, and the electronic LSD function is not likely working (like using a DCCD center diff without a controller). But I'm not sure exactly. This is my understanding as well - mechanically the parts swap and function. But electronically I’m not sure the TCU is capable of controlling the VTD properly. It may end up triggering the AT light. Edited November 5, 2021 by idosubaru Link to comment Share on other sites More sharing options...
Muskiefshr Posted November 6, 2021 Author Share Posted November 6, 2021 20 hours ago, idosubaru said: This is my understanding as well - mechanically the parts swap and function. But electronically I’m not sure the TCU is capable of controlling the VTD properly. It may end up triggering the AT light. Yeah, pretty much the same stuff I’ve been reading. I think what I’m going to try for the sake of getting a running driving car with the parts I have is swap the MPT center diff into the VDC trans to hopefully get a working trans. I know it won’t be as good as the VDC diff, but it will work and still have AWD capabilities. I haven’t pulled the pans yet to compare electronics on the valve body, but everything I read online and looking at the external wiring says that it should be compatible. I’ll keep all the VDC parts on the shelf and try to salvage as much of the VDC components out of the burned car as I can. Maybe one day I’ll tackle a full VDC swap. Link to comment Share on other sites More sharing options...
wavekayaker Posted April 15 Share Posted April 15 Muskiefshr, did you ever do the tailhousing swap? Looking at the same thing with a VDC to non-vdc tail housing. Link to comment Share on other sites More sharing options...
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