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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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 Posted: Sun Nov 19, 2017 1:14 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| pbrown wrote: |
The Syncro gearbox has a 1st gear of 3.78
...
The 03 Subaru WRX gearbox has the following ratios.
1st -- 3.454 |
that makes 1st on the WRX 9% taller than a syncro 1st.
add the tallness of the tire size to get some idea. For example, a 28" tire popular with many syncro owners, is 10% tall
the combo would be 19% tall. that is NOT a suitable gearing for "trail running" imnsho.
I also want DClymer to succeed, and I think his comments are very fair and reasonable as to what the Subie tranny is and is not good for.
get some idea of the percentages so you can make an informed decision...
a 27" tire is 6% tall
a 28" tire is 10% tall
Imo you should NOT choose the WRX tranny for a Syncro, because 1st is too tall, taller than the other option, which is 6% tall.
even with the 6% tall Subie, I don't recommend going past 27", that means
No 215x75x15, and
No 215x70x16, nor larger.
| pbrown wrote: |
| I'm sure that there are Syncro owners that never use the G gear. |
that is a good point, it might be part of a useful rule of thumb
I agree that there are some people that also never use a Locker. And Imo, people generally only use a Locker in Granny. Some people also don't drive on Unpaved roads.
So, for people who never use granny, never use a locker, and never have their Syncro on 3 wheels, the 5MT with 27" tires might be a reasonable match. Especially if they only drive on paved roads or smooth graded dirt roads that do not require granny, nor lockers.
also Imo the Subie AWD system is far superior to the Syncro VC, on pavement.
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human compass
Samba Member
Joined: June 04, 2013
Posts: 423
Location: Flagstaff,AZ
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| Posted: Sun Nov 19, 2017 5:02 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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sorry, was tired when I wrote this. didnt see that you had already discussed the 4.86.
cheers!
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84 Westy Syncro- 3.3L SVX stage 2 tune,subaru gears 6speed with tbd, front locker, porche brakes x4, aux tank, radflo susp |
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D Clymer
Samba Member
Joined: December 22, 2005
Posts: 2978
Location: Issaquah, WA
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| Posted: Sun Nov 19, 2017 10:15 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Jon_slider wrote: |
I also want DClymer to succeed, and I think his comments are very fair and reasonable as to what the Subie tranny is and is not good for.
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Thank you, Jon. Much appreciated. 
| Jon_slider wrote: |
So, for people who never use granny, never use a locker, and never have their Syncro on 3 wheels, the 5MT with 27" tires might be a reasonable match. Especially if they only drive on paved roads or smooth graded dirt roads that do not require granny, nor lockers.
also Imo the Subie AWD system is far superior to the Syncro VC, on pavement. |
There is a lot of wisdom here. The Subaru AWD trans in a Vanagon has a place for those who want a Vanagon with greatly enhanced traction, but don't plan to take their vans where the Vanagon's innate lack of suspension articulation becomes a limitation.
But even for back country dirt roads that are rough, loose, and steep, it's important to maintain a suitably low first gear. That's why I brought up the point about the taller first gear in the Subaru 5 speed transmission. That seems to get overlooked often when people are planning the specifications of their drivetrain.
My own Subaru 5 speed 2wd van with a torque biasing differential has brought me into some pretty impressive places over the last few years. It has a 4.86:1 final drive with the Subaru 3.45:1 first gear. This combination with stock sized tires (25.3") has a usefully low first gear, but I wouldn't want the gearing to get any higher due to significantly larger tires.
And, yes, the Subaru AWD system itself is great. It's full-time 50/50 AWD with a viscous limited slip function on the mechanical center diff. |
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D Clymer
Samba Member
Joined: December 22, 2005
Posts: 2978
Location: Issaquah, WA
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| Posted: Sun Nov 19, 2017 10:26 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| pbrown wrote: |
There is an 04 STI 6MT with the following ratios. It could be a good Vanagon option but I don't know if the Syncro option works on the 6MT.
1st -- 3.636
2nd -- 2.375
3rd -- 1.761
4th -- 1.346
5th -- 0.971
6th -- 0.756
I have not done the math on these to determine final drive with bigger tires. I'm still at least a year away from having to choose which transmission to use. I have two Syncro boxes and one is a locker. I'll likely use my locker for now but I'm really interested the the SubaruGears option and want them to be successful. |
Unfortunately, the STI transmission is a completely different design and it can't be reversed for use in a Vanagon.
There are two common 1st gear ratios for the split-case Subaru 5MT. The early transmissions use a 3.54:1 first gear. In about 2005 Subaru went to a slightly taller 3.45:1 first gear. It's not a huge difference, but worth noting nonetheless. There is actually a third choice that was used on the 2006 and later WRXs and Legacy GTs. It's like 3.16:1, so way too tall for any Vanagon application.
There are a few Subaru AWD converted Vanagons running around now, so hopefully the owners will share their impressions with us here. |
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Sun Nov 19, 2017 10:27 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| D Clymer wrote: |
| a 4.86:1 final drive with the Subaru 3.45:1 first gear. This combination with stock sized tires (25.3") has a usefully low first gear, but I wouldn't want the gearing to get any higher due to significantly larger tires. |
your first is 9% tall and your tire is 1% short, net 8% tall
I consider 10% tall overall is a practical limit
the thing is, when people think of an AWD syncro, not only do they not take into account the 1st gear, they fail to consider tire size.
Many syncros use 28" (10% tall) tires. I think that would be a bad combo on dirt, with your 9% tall first. I don't even think it is reasonable on pavement. Not even with a stronger than stock motor.
| D Clymer wrote: |
There are a few Subaru AWD converted Vanagons running around now, so hopefully the owners will share their impressions with us here. |
I hope to learn from them too, with tire size, gearing, horsepower, and driving conditions info
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D Clymer
Samba Member
Joined: December 22, 2005
Posts: 2978
Location: Issaquah, WA
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| Posted: Sun Nov 19, 2017 10:36 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Jon_slider wrote: |
| D Clymer wrote: |
| a 4.86:1 final drive with the Subaru 3.45:1 first gear. This combination with stock sized tires (25.3") has a usefully low first gear, but I wouldn't want the gearing to get any higher due to significantly larger tires. |
your first is 9% tall and your tire is 1% short, net 8% tall
I consider 10% tall overall is a practical limit
the thing is, when people think of an AWD syncro, not only do they not take into account the 1st gear, they fail to consider tire size.
Many syncros use 28" (10% tall) tires. I think that would be a bad combo on dirt, with your 9% tall first. I don't even think it is reasonable on pavement. Not even with a stronger than stock motor. |
Yeah, I agree with most of what you're saying. But sometimes all the calculations in the world can't predict how things work when you actually fire up the test mule for the first time and try to drive it. When I built the original Subaru 5 speed prototype 2wd van, I had settled on a 4.44:1 final drive ratio as perfect for the 3700 lb van with Subaru EJ25 torque curve. At the time, all I could get was a 4.11:1 final drive set. I put it in there to get the van up and running and prove the mechanical concept, but fully expecting that the van would be hopelessly overgeared. To my surprise, the 4.11 final drive was wonderful and allowed the van to move out smartly with traffic. It has become the ratio I recommend to most 2wd tin-top van owners. |
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flomulgator
Samba Member
Joined: March 07, 2013
Posts: 951
Location: Leavenworth, WA
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| Posted: Mon Nov 20, 2017 12:01 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Jon_slider wrote: |
| flomulgator wrote: |
I have a friend who had a EG33 paired to a 3.9:1 final drive Subagears 2WD, and it ran fine with 27" tires and returned over 20 mpg.
… he was tackling serious trails and the clutch burning was too much trying to keep speed low in 1st |
Burning the clutch is not what I call running fine.
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It was a fine runner on pavement. When he took the 3.9:1 to some seriously steep dirt tracks is where the problems occurred.
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Mon Nov 20, 2017 12:32 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| flomulgator wrote: |
| Jon_slider wrote: |
| flomulgator wrote: |
I have a friend who had a EG33 paired to a 3.9:1 final drive Subagears 2WD, and it ran fine with 27" tires and returned over 20 mpg.
… he was tackling serious trails and the clutch burning was too much trying to keep speed low in 1st |
Burning the clutch is not what I call running fine.
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It was a fine runner on pavement. When he took the 3.9:1 to some seriously steep dirt tracks is where the problems occurred. |
good distinctions
he found 25% taller than stock gearing with a 230 hp motor ok on pavement, but not on dirt.. makes sense.. way tall gearing
I know someone who enjoys their 16% tall gearing on pavement with a 180 hp 1.8t
and I know someone that liked 19% tall on pavement, and prefers 9% tall for steep dirt, with a 160hp 2.5 Subie
so yes, the motor power can make up for double digit tall gearing, if the van only goes where 2wd can go
imo the suby 5MT tranny is a best match for 2wd, and not suitable for syncros that use their granny gear
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gears
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Joined: October 28, 2002
Posts: 4391
Location: Tamarack, Bend, Kailua
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| Posted: Mon Nov 20, 2017 10:26 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Jon_slider wrote: |
| .. I also want DClymer to succeed, and I think his comments are very fair and reasonable as to what the Subie tranny is and is not good for .. |
I echo these sentiments. David has invested a heck of a lot of time in these conversions, and his attention to detail is self evident. I've even considered this for my own tin top.
I'm hoping that anyone going this route with their Syncro will sell their old transaxle to me. My goal is a completely reliable Syncro transaxle, maintaining the coveted G gear .. but I see a shortage of decent core transaxles as a potential stumbling block.
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D Clymer
Samba Member
Joined: December 22, 2005
Posts: 2978
Location: Issaquah, WA
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| Posted: Tue Nov 21, 2017 9:00 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| gears wrote: |
| Jon_slider wrote: |
| .. I also want DClymer to succeed, and I think his comments are very fair and reasonable as to what the Subie tranny is and is not good for .. |
I echo these sentiments. David has invested a heck of a lot of time in these conversions, and his attention to detail is self evident. I've even considered this for my own tin top.
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Thank you, Paul. That means a lot.  |
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WLD*WSTY
Samba Member
Joined: November 04, 2009
Posts: 438
Location: Arizona
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| Posted: Wed Nov 22, 2017 11:39 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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I'm curious if one might use just the Soob center diff in an otherwise stock Syncro, to better perform the function of the VW VC? A solid shaft would be necessary in the front diff of course.
Edit: Too much early Thanksgiving celebrating. A Syncro trans doesn't have enough shafts... 
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D Clymer
Samba Member
Joined: December 22, 2005
Posts: 2978
Location: Issaquah, WA
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| Posted: Wed Nov 22, 2017 11:56 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| WLD*WSTY wrote: |
| I'm curious if one might use just the Soob center diff in an otherwise stock Syncro, to better perform the function of the VW VC? A solid shaft would be necessary in the front diff of course. |
There's a fundamental difference between a full time AWD transmission like a Subaru or Audi Quattro transmission and an on demand AWD transmission like the Syncro. With an on demand AWD trans, the output for the center driveshaft comes directly off of the driven shaft that also spins the differential inside the transaxle. With a full time AWD trans, the driven shaft spins a center differential with one output going to the center driveshaft. The other output goes to the differential inside the transaxle. The function of a pure viscous coupling works with an on demand type of trans, while the Subaru center diff is designed to work with an full time AWD trans. The two units do look pretty similar when you see them both, but they are internally completely different. |
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Waldi
Samba Member
Joined: February 28, 2014
Posts: 1752
Location: Germany
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| Posted: Thu Nov 23, 2017 3:50 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| WLD*WSTY wrote: |
| I'm curious if one might use just the Soob center diff in an otherwise stock Syncro, to better perform the function of the VW VC? A solid shaft would be necessary in the front diff of course. |
If the center diff + VC would be better, Porsche, Audi, Lambo and VW would have used it.
You would have more weight and more turning parts without better performance.
Calling a center diff without locking or VC in hump mode a 50/50 awd is a bit irritating.
A center diff will not transfer 50/50 torque to both axels if 1 or 2 tires of 1 axel is slipping.
Only after the VC gets in action due to rev difference, it will transfer the torque up to 50/50 in hump mode.
So this is also a on demand 50/50 awd. As every VC controled system.
Only a locked (electronical or manual) center diff, or a Syncro with solid shaft is a full time 50/50 awd.
Imagine the rear diff (or front diff on a Syncro).
Left side is the front, and right side is the rear.
Without the 40% LSD (or VC) the torque is going to 1 wheel which loose contact to the street.
Edit:
The only reason why the Syncro VC system is not used nowadays in comon cars are the need of esp and abs for "ladys" 
https://books.google.de/books?id=zknjCAAAQBAJ&...mp;f=false |
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flomulgator
Samba Member
Joined: March 07, 2013
Posts: 951
Location: Leavenworth, WA
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| Posted: Thu Nov 23, 2017 12:10 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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Don’t be sexist, Waldi.
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Waldi
Samba Member
Joined: February 28, 2014
Posts: 1752
Location: Germany
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| Posted: Thu Nov 23, 2017 1:45 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| flomulgator wrote: |
| Don’t be sexist, Waldi. |
Sorry, i am not.
I am not your president |
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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
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| Posted: Fri Nov 24, 2017 8:52 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Quote: |
| Calling a center diff without locking or VC in hump mode a 50/50 awd is a bit irritating. A center diff will not transfer 50/50 torque to both axels if 1 or 2 tires of 1 axel is slipping. |
Most people are burdened with this common misconception about open differentials. I used to accept it myself, because everyone said so, until I spent a few minutes thinking about how a differential works, when it became obvious that it was wrong. Ridding yourself of this notion is necessary to understand driveline dynamics.
Tattoo this on your brain: An open differential, spur gear or planetary, center or axle, transmits exactly equal torque to both output shafts at all speeds and in all conditions.
It doesn't matter how much torque the engine can produce, force applied is limited to what can be absorbed. So people think an open diff is "one wheel drive" because the maximum torque that can be applied is limited by the tire with the lowest traction. If it takes less torque to make any one tire slip than the torque required for any tractive tire to move the vehicle, the tractive wheel across the differential will only receive that same amount of torque as the slipping tire, and the car doesn't move. The same balance and limitation of force applies across a center diff.
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Sodo
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Joined: July 06, 2007
Posts: 9615
Location: Western WA
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| Posted: Fri Nov 24, 2017 11:11 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| tencentlife wrote: |
Tattoo this on your brain: An open differential... transmits exactly equal torque to both output shafts at all speeds and in all conditions.
....If it takes less torque to make any one tire slip than the torque required for any tractive tire to move the vehicle, the tractive wheel across the differential will only receive that same amount of torque as the slipping tire, and the car doesn't move. |
Perhaps ---- "doesn't move". Description is "more valid" for a rear wheel elevated (not touching the ground) than for "slipping".
A slipping tire that's on the ground will have some forward force, and that torque applied to the other tractive tire is additive - thus two wheels are pushing forward somewhat. Drivetrain losses (friction) is a torque that's ADDED to the non-slipping wheel too, increasing the DRIVE. The tire with traction receives torque EQUAL to the slipping tire (plus frictions which could be 5%). One tire is spinning and stuff, but the non-spinning tire is providing EQUAL forward force. The name "one wheel drive" is a misnomer. It's "not a one-wheel drive," it's still two wheel drive. A better description is "one wheel slip".
This subject is very difficult to describe with typing. I'll try repeating it a little different to help understand what 10c wrote.
An open differential transmits equal torque to each wheel, always. If one wheel has little traction then the other wheel gets equal torque (= little). If one wheel is lipping in the mud, "a little" torque goes to the other wheel, not always enough to mover the car though. But note that if one tire is lifted off the ground - it has zero traction - the other wheel gets zero torque (equal). Actually it gets a little torque, it gets the "drivetrain losses".
This gets a little harder to understand with an "AWD open center diff" WRT the subject. If any of the four wheels has "little traction", then the other three wheels will receive "little" torque. So if one front wheel is in the mud and has "little traction", only "little torque" is transmitted to other 3 wheels. If one wheel is lifted off the ground, then the other 3 wheels receive zero torque, and the car stops. This works OK on even ground, fails miserably if un-even or if one wheel is in the mud. Like if you get one wheel in the ditch, you're stuck.
But WRT to the subject, Subarus don't have "open center diffs," don't they have at least a VC or limited slip in the center?
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Sat Nov 25, 2017 12:25 am Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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| Sodo wrote: |
| WRT to the subject, Subarus don't have "open center diffs," don't they have at least a VC or limited slip in the center? |
Yes
Subaru MT viscous coupling locking center differential:
http://www.awdwiki.com/en/subaru/
Syncro VC
https://shufti.blog/2010/04/02/viscous-coupling-hump-condition/
https://www.thesamba.com/vw/forum/viewtopic.php?p=8610494#8610494
| D Clymer wrote: |
| All of the Subaru 5MT and split-case 6MT center differentials are standard mechanical differentials with a small viscous coupling integrated that acts as a limited slip medium if the velocity of one axle significantly speeds up relative to the other one. There is a certain amount of allowance built into this viscous lock that allows the vehicle to be steered on pavement without it locking the diff. Regular 5 speed AWD Subaru cars turn nicely on pavement without binding. |
https://www.thesamba.com/vw/forum/viewtopic.php?p=8619296#8619296
| D Clymer wrote: |
There's a fundamental difference between a full time AWD transmission like a Subaru or Audi Quattro transmission and an on demand AWD transmission like the Syncro. With an on demand AWD trans, the output for the center driveshaft comes directly off of the driven shaft that also spins the differential inside the transaxle. With a full time AWD trans, the driven shaft spins a center differential with one output going to the center driveshaft. The other output goes to the differential inside the transaxle. The function of a pure viscous coupling works with an on demand type of trans, while the Subaru center diff is designed to work with an full time AWD trans. The two units do look pretty similar when you see them both, but they are internally completely different. |
https://www.thesamba.com/vw/forum/viewtopic.php?p=8610701#8610701
| D Clymer wrote: |
| The Subaru AWD system with 36/64 dynamic split is not the one used in these 5 speed and 6 speed cable shift transmissions. The one used in these basic manual transmission cars is "Continuous AWD." It's the original Subaru full-time AWD system that dates back to 1987. It's a completely mechanical system with a 50/50 dynamic torque split through a viscous limited slip mechanical differential. If you drive a Subaru Forester, Legacy, or Impreza with this system, it doesn't bind to any perceptible degree. |
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FrankenSubySyncro
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Joined: May 03, 2007
Posts: 638
Location: Vancouver, WA.
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| Posted: Mon Nov 27, 2017 6:20 pm Post subject: Re: New Build Thread: Subaru 5MT AWD into Syncro Vanagon |
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I bought the 4.86 syncro kit yesterday. Are there any build threads of completed subarugears awd conversions? How is the trans mounted with the awd?
I will be doing this to an 87 Wolfsburg that will have an svx and syncro conversion.
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