Need help selecting the right OB / engine

[Numbchux]

5 minutes ago, softroader said:

I'm lost here.  What does this mean?

The MPT cars are a FWD transmission, using a hydraulically-controlled clutch pack to send power to the rear. No pressure on that clutch, no power to the rear axle.

The VTD cars have a true mechanical center diff, with spider gears, sending power to both front and rear. They use the exact same clutch discs as the MPT, but their function is only to limit slip, not as the sole transfer of torque.

 

Example, it's very well documented with some basic wiring modification to lock up those clutch discs on an MPT car. I tried the same thing on our VDC, and cannot tell the difference. Have they failed? Is the layout so effective that it doesn't matter? I'm really not sure.

[softroader]

On 10/14/2020 at 2:54 PM, Numbchux said:

[...] Good used transmissions are very reasonable. Even for my VDC, I could get one for less than $1k [...] there are plenty of good used transmissions.

[...] If price and condition were no object, it would be a 2003 VDC in Forest Green, or 2004 in Black (I love the solid black look, but not a fan of the On-star and non-adjustable LH defrost vent, but those can be changed).

How much could I expect to pay for a good used 4AT transmission with VDC?  Without VDC?  Or a 5MT?

Why are the 2003 VDC or 2004  the ones you would want?  What's the deal with the non-adjustable LH defrost vent?  Which cars have that?

[softroader]

8 minutes ago, Numbchux said:

The MPT cars are a FWD transmission, using a hydraulically-controlled clutch pack to send power to the rear. No pressure on that clutch, no power to the rear axle.

The VTD cars have a true mechanical center diff, with spider gears, sending power to both front and rear. They use the exact same clutch discs as the MPT, but their function is only to limit slip, not as the sole transfer of torque.

Example, it's very well documented with some basic wiring modification to lock up those clutch discs on an MPT car. I tried the same thing on our VDC, and cannot tell the difference. Have they failed? Is the layout so effective that it doesn't matter? I'm really not sure.

Thank you, so much to learn here.  So that raises a question: I'm picturing the center diff as having a similar function to say a rear diff, where one wheel can turn faster than the other in turns... similarly with a center diff, one axle might turn faster than the other (which the MPT will try to compensate for).  Hopefully this is correct so far...  So, with the MPT inactive (with the VDC system failed, or disabled), would the AWD system be able to tolerate having a (temporaily) mismatched tire without overheating like the viscous coupler in MT models?   

[idosubaru]

20 minutes ago, softroader said:

So, with the MPT inactive (with the VDC system failed, or disabled), would the AWD system be able to tolerate having a (temporaily) mismatched tire without overheating like the viscous coupler in MT models?   

Pandora's box discussion. 

Due to the functionality you mentioned it's possible to have two bald tires and two brand new ones on non-LSD rear diff subarus.  install one new one up front and one new one on the rear...usually the opposite side rear - though that's for traction I presume and not differential reasons.  there are tire shops in low economic areas that do it.  The problem is the front driven wheel will be the small one - so you're already bald tires will wear faster than the new ones.  But it can be done as a work around or to buy some time, etc. 

Yes they can tolerate mismatched tires *somewhat*....but it depends what you mean by "temporarily" and "mismatched" - do you mean slightly different tread depth, different brands, running a spare, or waaaaay different tire sizes?

Many auto's use that functionality you reference, for the FWD fuse. They come stock with a FWD fuse holder from the factory that's empty.  insert a fuse and you have FWD.  The VDC's don't have this circuit but you're asking about MPT's. So yes it "can" tolerate it but it depends what you mean....how bad, why, what circumstances, how long - do you mean as-is tolerate, or do you mean with some effort?   Force it into FWD or install a switch and run whatever tires you want. 

Which means you can also install your own switch/wiring to go from FWD to nominal ops to "locked". 

And for all of those reasons and more - it's generally simpler to just say - "buy mismatched tires".  But there are options for those with some mechanical understanding or willing to ask and find out what they're options are.  For those willing to learn - the hard part is knowing who to listen too.  This is probably the best forum to do so - the others are full of inexperienced anecdotal commentary that's hard to navigate if you're unfamiliar. Most folks spouting off have never even looked inside a trans or repaired them or tried any mismatching tires and have actual data to go on.  They're just regurgitating Subaru talking points - which is good for the general public. If you're asking these questions - you aren't the general public. 

From there it gets into a loooong discussion about nuance - how long, how different, does it matter, and most opinions are going off anecdotal reports or gut feelings with zero experience.  There's an entire tribe of people who swear your trans will Little Boy if tires aren't matched perfectly, quote subaru spec's, and declare as if the laws of nature are written by subaru tech's that these mystical "engineers" designed it that way and it should never be questioned. 

And as a general one-size-fits-all rule - that has very strong merit. But there are options and the auto's can be forgiving. 

I've run tons of Subarus over a quarter century on mismatched tires and have never had issues.  I wouldn't do it on modern EJ manuals, the older gen manual trans seem to almost never have issues, i've seen one potential case in 25 years.   I've seen meticulously maintained low mileage one owner Subarus get torque bind.  They're so old that tens or hundreds of thousands of rusty ones aren't worth the cost of 4 new tires and people routinely do wonky tire stuff to old rusty subaru's.  they're just not posting about it and pontificating it all day long. they're just getting by day to day.  and for all of that - the difference is striking between how many issues they incur (like zero - or not a signfiicantly greater than average amount) - compared to what internet lore might suggest.  I'm pretty abusive to some of my mine - and i'm surprised how few of those in the general public like that which are all but ignored except as cheap daily drivers - never have isseus.  There's no hard and fast rules but clearly they can be very forgiving in general - and they're very forgiving if you can pay a little attention. 

 

Edited October 16, 2020 by idosubaru

[softroader]

41 minutes ago, Numbchux said:

The VTD cars have a true mechanical center diff, with spider gears, sending power to both front and rear. They use the exact same clutch discs as the MPT, but their function is only to limit slip, not as the sole transfer of torque.

 

5 minutes ago, idosubaru said:

Pandora's box discussion. 

[...]  The VDC's don't have this circuit but you're asking about MPT's.

[...] But there are options for those with some mechanical understanding or willing to ask and find out what they're options are.  For those willing to learn - the hard part is knowing who to listen too.  This is probably the best forum to do so [...] If you're asking these questions - you aren't the general public. 

From there it gets into a loooong discussion about nuance - how long, how different, does it matter, and most opinions are going off anecdotal reports or gut feelings with zero experience.  [...]

I've come to the right place then.  Yes, willing to ask, and very willing to learn.  I am an engineer, anecdotes are sometimes useful but what I really want to hear is knowledge from those with actual experience, real data.  A good example is the recurring question of whether the EJ25 head bolts are torque to yield or can be reused.  The FSM says they can be reused.  So that's the correct answer.  But the tribal skirmishes keep happening over it regardless of the fact.

Anyway, I actually was asking about the VDC system, not the MPT.  Sorry, I wasn't clear in my question, I should have written "which the clutch discs will try to compensate for" instead of "which the MPT will try to compensate for".

The scenario would be temporarily installing a spare tire, which for whatever reasons might not match in diameter or tread type etc, to extract from an offroad situation and drive, perhaps a few hundred miles, back home or to where a matching tire could be obtained.  What I'm curious about is whether, with the VDC system temporarily disabled, the AWD system would tolerate the mismatched tire on one axle because the center differential, being a differential, inherently wouldn't mind the difference in front vs rear axle rotation rates.  I'm curious because (a) I want to understand how this system works and (b) the vulnerable and always connected viscous coupling in the MT Outbacks makes me uneasy in this scenario.

Loved your Little Boy comment!  Totally agree about Subaru marketing dogma, and those who regurgitate it.  I'd much rather understand te system and be able to make fact/knowledge based decisions.

[softroader]

36 minutes ago, idosubaru said:

I've run tons of Subarus over a quarter century on mismatched tires and have never had issues.  I wouldn't do it on modern EJ manuals, the older gen manual trans seem to almost never have issues, i've seen one potential case in 25 years.

I've seen meticulously maintained low mileage one owner Subarus get torque bind. 

Does "modern EJ manuals" include the 2001-2004 Gen 2 OBW?  I'm asking because I'm going to see one that's for sale today.  A 2002 5MT.

Why did those cars get torque bind?  What failed and what caused it?  Is it certain years/models I should be avoiding?

[Numbchux]

1 hour ago, softroader said:

How much could I expect to pay for a good used 4AT transmission with VDC?  Without VDC?  Or a 5MT?

Why are the 2003 VDC or 2004  the ones you would want?  What's the deal with the non-adjustable LH defrost vent?  Which cars have that?

www.car-part.com, take a look in your area.

Here's the driver's side defrost vent. on the '00-'03 ones (and previous body styles), it can be flipped between sending air along the LH window or to send extra onto the windshield right in front of the driver. I'm driving a 2004 these days, and boy was I wishing I had it this morning (25*F), I'll probably steal it from my '00 parts car.

20170211_104858 by Numbchux, on Flickr

 

Mid-2002 got a front brake size upgrade and center console change. 2004 VDCs all have on-star. All minor things that are easy enough to change (I have swapped all of those things one way or the other on all my cars), but if I were to pick one that's as close to perfect as it can be out of the box, it'd be a 2003.

 

1 hour ago, softroader said:

Thank you, so much to learn here.  So that raises a question: I'm picturing the center diff as having a similar function to say a rear diff, where one wheel can turn faster than the other in turns... similarly with a center diff, one axle might turn faster than the other (which the MPT will try to compensate for).  Hopefully this is correct so far...  So, with the MPT inactive (with the VDC system failed, or disabled), would the AWD system be able to tolerate having a (temporaily) mismatched tire without overheating like the viscous coupler in MT models?   

The FWD fuse on the MPT models is exactly for that purpose. No such function exists on the VDC ones.

Edited October 16, 2020 by Numbchux

[softroader]

7 minutes ago, Numbchux said:

www.car-part.com, take a look in your area.

Mid-2002 got a front brake size upgrade and center console change.

Was part of that change the twin cup holder vs single?  I'm looking at a 2002 OBW today that (from the pics) has a twin cup holder, so will that mean it also has the front brake size upgrade?

[Numbchux]

It's about the same time, but I don't know if it's the exact correlation. And occasionally, if a shop bought pads/rotors/calipers, they might convert the car from one system to the other without knowing.

[GeneralDisorder]

Just get a non-VDC 4EAT 2000 to 2004 Outback or Forester. 

VDC transmissions are difficult to find replacements for. 

As for running a mismatched tire for a few miles - it's not going to be a problem in practice. Drive slow. Make frequent stops. These cars are HEAVILY abused at this stage of their life and the transmissions just aren't failing from the current level of ownership - which is by and large people without money for good tires, or even complete matching sets of tires. The auto's really don't care much. The manual's suffer from center diff failure on the regular - local dealers stock about 3 of each MT center diff at all times to keep from being out of stock. Coupled with the clutch, and the lack of a low range (provided by the auto's TC), they are a poor choice. Especially for off road. 

The EZ30's go about 175k to 225k and lose HG's. Once they go you can replace the engine cheaper than you can replace the HG's. They aren't all that much more powerful, and the parts for them are more expensive, and they are a lot more labor intensive. Personally I feel they are a poor investment. Subaru will orphan them sooner than the 4 cylinder. Subaru has now discontinued all H6 engine models. 

GD

Edited October 16, 2020 by GeneralDisorder

[softroader]

5 minutes ago, GeneralDisorder said:

Just get a non-VDC 4EAT 2000 to 2004 Outback or Forester.  VDC transmissions are difficult to find replacements for. 

As for running a mismatched tire for a few miles - it's not going to be a problem in practice. [...] the transmissions just aren't failing [...] The auto's really don't care much.

The manual's suffer from center diff failure on the regular [...] clutch, and the lack of a low range [...], they are a poor choice. Especially for off road. 

The EZ30's go about 175k to 225k and lose HG's. Once they go you can replace the engine cheaper than you can replace the HG's. [...] Personally I feel they are a poor investment.

GD

Great info, thank you.  No longer sure it makes sense to get the EZ30 OBW with its DOHC headaches, expensive parts, cheaper to swap in a JDM EZ30 ($1200) vs replace the HG's (ouch!), all for an extra ~45HP and ~45ft-lbf torque (and a heavier vehicle) ... and most 2001-2004 H6's for sale around here seem to be right in the "175k to 225k and lose HG's" range so it would be a ticking time bomb.

No longer sure it makes sense to get the 5MT either with those common center diff failures, and no way to know the car's real history... maybe it was run on mismatched tires for years and damage already done that wouldn't show up on a short test drive without fully warming up the viscous coupler... and I do plan to do a lot of offroading (softroading, nothing gnarly) in this Outback.

Looks like the sweet spot is the 2001-2004 EJ251 4EAT MPT, and just deal with the timing belt (easy) and head gaskets (not difficult) when the time comes.  My assumption coming into this, after having driven 4-cylinder cars with AT's years ago, is that if I bought an H4 4EAT OB I would be buying a snail that couldn't get out of its own way, but the 2001 H4 4EAT I test drove a couple of days ago didn't seem like that at all, and there are a lot of H4 AT OB's out there whose owners seem satisfied with their performance, even in mountain states.  Guess I need to drive another one to make sure, then grab the first good one that comes along.

[GeneralDisorder]

They have reasonable power for what they are. Not nearly *enough* power IMO, but then everything I drive these days has at least 350 HP, and you get spoiled driving high HP race cars all the time.

They will get down the road, up mountains, and they don't feel like everyone is going to run you over. But they certainly aren't fast. 

GD

[1 Lucky Texan]

I think for an enthusiast with some time/money on their hands, or someone with a race whip, there may be some utility in experimenting with gear lubes - maybe moreso if you live in the SW or extreme north, further tailoring the lube chosen for extreme temps.

but, the OEM lube (Extra-S ? made by Idemitsu I think) or a name brand non-synth lube probably works fine for most people. If you have a leaky, or older car and no money to spend, there is a synth-BLEND at walmart (supertech ?) that folks feel is a good value. Local tuner shop (the guys that fixed my trans) use Amsoil Severe Gear 75W90 . It's still in there. feels OK to me. BUT, I also had to rebuild my shifter and since putting in new poly bushings, kinda have the itch to try something new. But, not driving the car much right now - lost my job. I also have a feeling the trans prefer quicker shifting, seems like I get more balking if I'm slow about shifting - could be a lots of factors really.

 

if you want to go down a rabbit hole - try this link; https://forums.nasioc.com/forums/showthread.php?t=920674

 

[softroader]

3 hours ago, Numbchux said:

[...] it's very well documented with some basic wiring modification to lock up those clutch discs on an MPT car.

Numbchux, did you ever try hacking the TCU to add paddle shifters to the 4EAT?  I came across a thread from 2008 (yeah, I know) in which you were planning to try this on your XT6.  Did anything ever come of this?  I'm toying with the idea of doing this to my OBW when I finally find the one I want, it isn't necessary at all but it would be a really fun project.  I'm a EE/CS and have years of experience writing assembly language for embedded processors and operating system kernel code so taking on a TCU modification project like presslab's in that 2008 thread doesn't faze me in the least.  Though as I recall he had to make some hardware modifications to the AT, and I would not want to do that.

[softroader]

14 minutes ago, GeneralDisorder said:

They have reasonable power for what they are. Not nearly *enough* power IMO, but then everything I drive these days has at least 350 HP, and you get spoiled driving high HP race cars all the time.

They will get down the road, up mountains, and they don't feel like everyone is going to run you over. But they certainly aren't fast. 

GD

I get to drive a very high performance vehicle at work, so have no need to go fast in my car.  Especially since a suicidal deer decided to run in front of my DD in the mountains a couple of years ago, now I drive mountain roads at the speed limit or less, much to the annoyance of the drivers behind me who seem to think a twisting two lane blacktop with blind curves and sheer drop offs is an extension of the freeway.  Reasonable power should work fine for me.

I'm used to my DD which has over 400,000 miles on the original 22RE engine, which wasn't exactly a speed demon when it was newer... now, when I drive up that long grade on 395 from Bishop to Mammoth Lakes, I'm in the far right lane, 3rd gear, giving the engine as much gas as it can use, one eye on the temperature gauge and another on the rear view mirror watching the rapidly growing sight of a vehicle with more torque than mine as it gets ready to swerve past me mere feet from my bumper, horn blaring, middle finger extended, as though I chose to crawl up the grade as slowly as crankcase sludge on a cold winter morning.  I love my car, she gets me there, but that is no fun at all.

[GeneralDisorder]

TCU failures are a concern as the hardware is getting old. Have seen several 90's TCU crap out or throw erroneous codes.

GD 

[GeneralDisorder]

I would look into one of the many readily available 4L60E controllers. The Subaru 4EAT has a similar set of solenoids. You could control the rear output with a simple PWM controller or just shut it off for full 4WD or 100% for 2WD. 

GD

[softroader]

2 minutes ago, GeneralDisorder said:

TCU failures are a concern as the hardware is getting old. Have seen several 90's TCU crap out or throw erroneous codes.

GD 

That type of hardware usually lives a long time.  My guess is the failures are due to memory cell changes from high energy particles.  Same thing that occasionally causes computers and phones to need an unexplained reboot.  Reflashing the TCU should fix that.  If the memory cell is damaged not just flipped, the memory chip could be replaced and reflashed.  Or it could be a failed solder joint from vibration - my cruise control computer in the DD suddenly started to drop out at random times after working for years.  I resoldered every joint on the board (easier than finding the bad one), reflowed the conformal coating with some alcohol, let it dry and reinstalled.  It's been fine for years.

[softroader]

3 minutes ago, GeneralDisorder said:

I would look into one of the many readily available 4L60E controllers. The Subaru 4EAT has a similar set of solenoids. You could control the rear output with a simple PWM controller or just shut it off for full 4WD or 100% for 2WD. 

GD

Good idea, I'll look into that.

[softroader]

On a topic related to my looking for a good used 2000-2004 OB, I have a question about OBD-II Code Readers.  I have never used one, my DD predates OBD-2.  I need to buy one for my used car search to check for fault codes etc.

I'm looking at an OBD-2 reader that supports live data.  Live data would be very useful after I buy the car.

Does the 2000-2004 OB support live data on the OBD-2 port (oil pressure, AT fluid temperature, etc)?  I can't find this in the FSM.

Edited October 16, 2020 by softroader
Spelling

[Numbchux]

1 hour ago, softroader said:

Numbchux, did you ever try hacking the TCU to add paddle shifters to the 4EAT?  I came across a thread from 2008 (yeah, I know) in which you were planning to try this on your XT6.  Did anything ever come of this?  I'm toying with the idea of doing this to my OBW when I finally find the one I want, it isn't necessary at all but it would be a really fun project.  I'm a EE/CS and have years of experience writing assembly language for embedded processors and operating system kernel code so taking on a TCU modification project like presslab's in that 2008 thread doesn't faze me in the least.  Though as I recall he had to make some hardware modifications to the AT, and I would not want to do that.

No, I never did. Someone pulled out in front of me and wrecked the car...still have it and would like to use it as a dedicated RallyX car, but only need 1st for that. Also, I will probably get one of these for my 4Runner transmission, I think the Nissan/GM version would control a Subaru transmission just fine, and likely could be run in parallel to the factory TCU to retain AWD function.

 

For the record, the EJ 4-cylinder engine is at least as discontinued as the EZ 6-...Yes, the EJs are more common, but I've had no trouble getting everything I need for EZ30s. This isn't an EG33 or ER27.

 

I've been reading a lot about capacitor failure in '90s Toyotas (to the point that I replaced the 12 caps in my 1UZ ECU as part of swapping it into my 4Runner), and my '94 Ford 351 Van. I'm kind of curious to open up some Subaru control units and see what the caps look like in those. I haven't experienced any troubles like that, though.

 

Center diffs do fail, but it's not a terrible job to replace them (don't have to remove the transmission), and there's a guy in Europe that can rebuild them (even modify to be stronger) for a reasonable price.

 

Yes, you can read a bunch of live data through OBD II. Definitely can't read oil pressure (there is no sensor, just the switch for the idiot light), don't think there is transmission temperature either. But you can view ignition timing, fuel trims, coolant temperature etc. I have a cheap (<$20) dongle that I tether with my phone to read a ton of information.

Edited October 16, 2020 by Numbchux

[softroader]

17 minutes ago, Numbchux said:

 I think the Nissan/GM version would control a Subaru transmission just fine, and likely could be run in parallel to the factory TCU to retain AWD function.

I've been reading a lot about capacitor failure in '90s Toyotas (to the point that I replaced the 12 caps in my 1UZ ECU as part of swapping it into my 4Runner), and my '94 Ford 351 Van. I'm kind of curious to open up some Subaru control units and see what the caps look like in those. I haven't experienced any troubles like that, though.

I'll look into the GM units, which seem a bit expensive for what they are.  Or maybe just build something from scratch for the paddle shifters.  It doesn't have to do much, inputs are the paddle shifters and engine RPM, outputs are the 4EAT solenoids and maybe some lights.  The logic is simple, shift the tranny according to paddle commands, refuse to shift or upshift if engine RPM is too high.  And some smarts to make it play well with the TCU so it doesn't fight for control of the AT or cause the TCU to generate unneeded fault codes.

[softroader]

24 minutes ago, Numbchux said:

Yes, you can read a bunch of live data through OBD II. Definitely can't read oil pressure (there is no sensor, just the switch for the idiot light), don't think there is transmission temperature either. But you can view ignition timing, fuel trims, coolant temperature etc. I have a cheap (<$20) dongle that I tether with my phone to read a ton of information.

Thanks.  That makes sense.  The 2005+ CANbus cars presumably report everything and frames containing interesting parameters are flowing on the bus continuously.  But I don't want CANbus.

I added an oil pressure sensor to my DD.  I'll just do that to the OB too.  It drives an arduino which converts it to a signal that drives my oil pressure gauge and gets upset if the pressure is too low for the engine rpm.  And a few things like that.  Simple, and way more useful and responsive than the stock snail-slow gauge.  And way, way more useful than just an idiot light (it's really just a "too late" light).

[Numbchux]

3 minutes ago, softroader said:

I'll look into the GM units, which seem a bit expensive for what they are.  Or maybe just build something from scratch for the paddle shifters.  It doesn't have to do much, inputs are the paddle shifters and engine RPM, outputs are the 4EAT solenoids and maybe some lights.  The logic is simple, shift the tranny according to paddle commands, refuse to shift or upshift if engine RPM is too high.  And some smarts to make it play well with the TCU so it doesn't fight for control of the AT or cause the TCU to generate unneeded fault codes.

Yep, all way over my head, but probably doable. I think what made what presslabs did very cool, was adding it into the software on the factory TCU, and still retaining the factory automatic functionality. But with microsquirt and arduinos doing what they can these days, it would probably be infinitely easier to make a standalone controller.

[1197sts]

Regarding the twin cup holder, it began in the 2002 model year. It is a nice and easy upgrade to the '00 and 01 models, you just need the armrest piece (console) and the piece with the cupholders, it installs in place of the original single cup holder. In my area they are getting harder to find in the pick n pull but they go for about 15.00.

The brake upgrade started mid year 2001, I think the date is 10/01/2001.

Edited October 16, 2020 by 1197sts
correct info.