Kicking around a 4EAT MPT to VTD swap...

[casm]

Right, so. Even with the lockup mod in place, I don't much care for how the MPT in the 4EAT works. It's not that it doesn't work, but sometimes it feels a little too clever for its own good in my book. What I particularly dislike about it is that rather than starting from a 50:50 split (or close enough as doesn't matter), it's 90:10 and constantly readjusting. This drove me berserk in the snow this week because I'd set myself up in advance to plough through the conditions ahead only to be smacked down by the gearbox.

Anyhow, I'm thinking that the VTD may be a better choice. Admittedly, it still adjusts torque proportion of its own accord, but at least it starts from (more or less) 50:50. Coming from the world of vehicles with a traditionally-locked centre diff, this may be more to my liking in most usage

I've read through this thread over on SF.org, and while I've no issues with their approach, I'm wondering if the same thing can't be accomplished with a transmission swap. My assumption is that this would involve also getting the TCU from the VTD donor car and somehow making it work in my SF - but I can't see how that would be any different from what is essentially the tailcone swap they're talking about in that thread.

Has anyone tried this swap before, and, if so, what did you have to go through to make it work? Was the VTD TCU electrically- and pin-compatible with the loom in the Forester? Even if you weren't doing this on an SF, I'd be interested to know what hoops you had to jump through to get it going.

Note that I'm specifically avoiding anything with VDC capability. We have that in our OBW and I can't stand it. There's one specific patch of uphill, slightly off-camber trail that's a bit washboardy with gravel over it that always turns that car into a one-wheel-drive wonder because the computer can't work out what's actually going on.

 

[NachaLuva]

Sorry, whats MPT & VTD?

 

[Shiv]

Sorry, whats MPT & VTD?

Just for everyones reference, here's an explanation of both:

Electronically-controlled Multi-Plate Transfer Clutch

Subaru uses a Multi-plate Transfer Clutch System (MPT) on many of its automatic-equipped models for a combination of optimum traction and fuel economy. The system uses an electro-mechanical centre differential. Its control unit constantly monitors input from the Throttle Position Sensor (TPS), the Engine Control Module (ECM), the Transmission Control Module (TCM) and wheel speed sensors to provide the most effective front/rear balance of torque.

In good traction, the MPT’s predetermined logic splits torque 60/40 front/rear for enhanced fuel economy. In poor traction situations or under hard acceleration it can vary the balance up to a full 50/50 for maximum traction.

Variable Torque Distribution

Variable Torque Distribution (VTD) is a highly sophisticated system for automatic transmissions that combines an electro-mechanical centre differential with the advanced capabilities of a planetary gear set. The difference between VTD and MPT is significant—while MPT can vary torque between 60/40 and 50/50 front/rear, VTD provides the kind of performance experience usually associated with rear-wheel drive vehicles. In most conditions, the split is 45 percent front, 55 percent rear for an enhanced performance feel. In poor traction conditions, VTD can dynamically adjust up to a full 50/50 front/rear split.

When used with Subaru’s advanced Vehicle Dynamics Control (VDC), VTD has the flexibility to open the centre differential fully and direct engine torque to a single wheel. The VDC-equipped system works in tandem with the AWD system, Traction Control and ABS to provide outstanding stability control.

It'd be interesting to see if the swap can be done. Having owned both 4EAT and VTD, the VTD is a much sweeter drive.

Doesn't your Outback have a switch to just turn the VDC off?

 

[casm]

It'd be interesting to see if the swap can be done.

From what I've found, I think it can be - so far, the biggest hurdle I've found is that the TCU pinouts between my '99 and the (assumed) '05 donor car don't quite match, but I think that can be worked around. Not sure if the '05 will have CANBUS issues that may complicate things, though.

Having owned both 4EAT and VTD, the VTD is a much sweeter drive.

Agreed. What got me started on this line of thinking was driving an '05 Baja a while back with the VTD. It just worked better, IMHO.

Doesn't your Outback have a switch to just turn the VDC off?

Nope - AFAIK, US-model cars didn't have that in '07, but I believe some earlier ones did. It does, however, have a traction control switch, and I believe that does effectively the same thing - VDC is one of the systems disabled along with the traction control, IIRC.

 

[Rally]

Talk about over complicated! It would seem that the technology is directed more for on road use than offroad use. I don't know much about what auto Subaru's are like- think I'm glad my rather basic manual dual range works satisfactorily

 

[casm]

Talk about over complicated!

Dunno, it doesn't seem that bad to me - but then, I grew up driving Citroëns :biggrin:

It would seem that the technology is directed more for on road use than offroad use.

Bingo! That's exactly it.

I don't know much about what auto Subaru's are like- think I'm glad my rather basic manual dual range works satisfactorily

Problem is that Subaru hasn't offered a manual with dual-range in the US since the early '90s. There are a few later models that have been retrofitted with EA82 dual-range gearboxes, but those are getting hard to find and for something that's a daily driver more work than I'd want to get into.

The other consideration is that the 4EAT has lower gearing than the 5MT, which, in the absence of a low range, is a definite plus. I've considered the possibility of something like an electrically-switched version of a Klune V underdrive to make up for that, but for the amount of effort that would be I may just as well do the EA82 gearbox swap.

 

[fandizzle]

Has anyone had any luck with this swap?