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IdahoDoug Samba Member
Joined: June 12, 2010 Posts: 10252 Location: N. Idaho
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Posted: Wed Nov 26, 2014 12:02 pm Post subject: |
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Jon Slider sez:
"Basically the operator has to act like the VC, and only engage front diff in anticipation of when rear wheels would be spinning. "
This is perhaps the most accurate way to frame the issue of using a locked center device (either a decoupler or a locked center diff) on public roads. When traction is extremely poor, and your 4 tire contact patches are barely able to generate enough friction with the ground to accelerate or brake your Vanagon, the last thing they need is to be fighting each other. And yet when you lock them to each other, that is what happens unless you are driving perfectly straight ahead. Perfectly straight. Any deviation from perfectly straight and you are causing tension between the front and rear contact patches that ranges from mere mild pressure on a very gentle interstate curve, to easily felt slippage on a country lane curve.
And you are doing this when the contact patches are already having trouble doing their job of providing traction for steering, braking and accelerating.
So, understand that you are not helping the Van get around safely. The proper time on the road to use a locking feature (or decoupler) is when conditions are so bad you need the feature to accelerate from rest in deep snow or on slick ice or polished snow. But understand you are now generating speed that may be inappropriate to the available traction for braking, or steering. I get it that we are all engaged and sporty involved owners of unique vehicles and its fun to tromp on the gas and fishtail, etc. And I accept that.
And if you posit that on a snowy curvy lane where applying the gas in 2WD causes the rear tires to slip out, so you're going to engage the decoupler, then I say you are now possibly making a bad judgement call. You are adding to your acceleration abilities, while reducing your cornering abilities (because while locked the contact patches are now fighting on curves).
I get it that there are few things more fun that having the vehicle at the limit of adhesion and horsing around. But consider that for safe travel on the slippery road with a decoupler you may be better off in an overall sense to be unlocked.
It is also worth noting that if you are locked on a curve and lose control only slightly with the rear coming around, now you are definitely worse off than if you were in 2WD. Because you are essentially suddenly turning sharply like you would be in a snowy lot trying to park (which everyone acknowledges is the worst), but you have perhaps 35mph of vehicle momentum to deal with while fighting for control.
I'm sure that many will disagree, but if you do then you need to explain how you are on a curve and your contact patches are not fighting each other.
I have owned a few Audis over the years. My current one has a locking rear differential. The feature automatically unlocks at about 12mph in recognition of exactly the issues I am raising. A locked diff is at its best getting you going in deep snow or on ice. But it is at its worst when you are moving well down the road and now need to deal with curves. I'm sure that VW engineers went through exactly this reasoning when they opted for the viscous coupling. I personally went through this same reasoning at GM while working on the AWD VC system that eventually was used on the Pontiac 6000 STE AWD model. We did exhaustive research on artificial ice, took high speed photos of tire contact patches from under the road, etc.
So, don't be uninformed about the downside of locked devices on the road. On the trail - absolutely the best. And for fun on the road - the best. I am one of those who also finds an empty snowy road, locks up and does my best rally driver imitation with a huge grin on my face (and often a sprained thumb from frantically whirling the steering wheel from lock to lock). But know the limitations of these devices well for actual travel on public roads where the goal is safe travel. _________________ 1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader |
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gears Samba Member
Joined: October 28, 2002 Posts: 4391 Location: Tamarack, Bend, Kailua
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Posted: Wed Nov 26, 2014 10:30 am Post subject: |
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Corwyn wrote: |
I drove a 2nd in Fairbanks, Alaska for three years.
Rule #1: Ice is ice and 4 wheel drive won't make a difference. |
Corwyn, I assume you mean 2WD ..
Driving in Alaska for 3 years definitely makes you more experienced than I, however .. last snow season when I got stuck down a small rise with a balky decoupler on a black ice day, coaxing the system into AWD was the ONLY way I got out of a tight situation. The difference was immediate, and it was night & day. _________________ aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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Corwyn Samba Member
Joined: December 29, 2009 Posts: 2239 Location: Olympia, Washington
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Posted: Wed Nov 26, 2014 9:37 am Post subject: |
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I drove a 2nd in Fairbanks, Alaska for three years.
Rule #1: Ice is ice and 4 wheel drive won't make a difference. _________________ '90 White Westy ("The Longship")
FAS Gen V 2.0
The Annual Baja Rally
https://www.thesamba.com/vw/forum/viewtopic.php?t=604813&highlight=baja
"If anything's" gonna happen, it's gonna happen out there"
~ Captain Ron ~ |
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flomulgator Samba Member
Joined: March 07, 2013 Posts: 951 Location: Leavenworth, WA
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Posted: Wed Nov 26, 2014 8:59 am Post subject: |
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I've driven old-school (read: locked center) 4wd a lot on mixed snowy highways that patchwork from snow to pavement. The biggest difference in handling is that a locked center will understeer a bit more than a VC center because of the slipping issue (which shouldn't be as big on the short wheel base van as the long wheel base trucks I'm thinking of).
If you hit backwoods snowy roads where you're really fighting for traction, solid shaft is the way to go. If your cruising highways where seamless operation and dynamic stability are key, VC. If you want the best of everything for winter, aggressive VC with decoupler. _________________ She's built like a steakhouse, but she handles like a bistro! |
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alaskadan Samba Member
Joined: January 09, 2013 Posts: 1858 Location: anchor pt. alaska
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Posted: Wed Nov 26, 2014 7:33 am Post subject: |
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Dont let responses compare a locking front diff with being able to decouple an open diff from the rear. A locking diff is no good on snow or ice when locked. An open front diff with a solid shaft is the same a regular 4x4. As jon slider stated you have to be an aware driver and know when to use 4 wheel drive. I have a chevy k5 with detroit lockers front and back. When i have to drive it in snow im very carefull. Touch the gas and they lock. |
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Syncro Jael Samba Member
Joined: December 19, 2013 Posts: 2204 Location: Utah
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Posted: Wed Nov 26, 2014 7:29 am Post subject: |
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If you live in an area that has winter condition driving a lot an agressive VC or sport VC would be more desire able.
Off road in sand is where a solid shaft shines.
A VC is still nice to have because it keeps a little "give" in the drivetrain and less stress on the tranny.
If you off-road a lot the solid shaft might be your ticket. If you are on pavement most of the time then stay with a VC. Pulling the center knob in crosswinds on slick surfaces makes you feel all giddy inside. All wheel drive for winter driving. 4 wheel drive for off road. _________________ 1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat) |
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howardvw Samba Member
Joined: December 15, 2003 Posts: 73 Location: mostly the web
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Posted: Wed Nov 26, 2014 5:46 am Post subject: |
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i drive engaged solid shaft 90 percent once snow falls. if the highways been plowed real good with no black ice or wind kickup ill turn it off.
its supposed to be seamless so i cant tell the difference on or off on the highway= because it is seamless . but i am glad i have it on black ice patches and wind blowing with 20 temps going 55...so give it a pull. |
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Jon_slider Samba Member
Joined: April 11, 2007 Posts: 5091 Location: Santa Cruz, Crowdifornia
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Posted: Wed Nov 26, 2014 1:45 am Post subject: |
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IdahoDoug wrote: |
I have two vehicles with locking center diffs that when engaged allow me to compare how they behave on snowy conditions versus unlocked. No way would I say they are fine on snowy roads. On a snowy curve, they are completely unstable and I have to drive SLOWER than if unlocked. At any kind of speed, you are definitely running wide and the vehicle changes attitude constantly as you run on and off road surfaces with more traction, less traction and bare spots. By contrast, when unlocked these same curves at the same speeds are uneventful. |
I agree that a solid shaft should only be coupled when the pavement is completely covered in snow and direction of travel is mostly straight.
Solid shaft imo should be decoupled on bare pavement unless going straight.
Generally speaking, on snow covered pavement, I decouple my solid shaft in turns, and especially when making tighter than say 45 degree turns. So I decouple pulling into a driveway or parking spot, even if the pavement is fully snow covered.
In patchy snow, I do not engage the front.
IdahoDoug wrote: |
When you are turning sharper slow speed corners such as when entering a parking lot, or turning at an intersection the slippage is far worse, simply because the % of slippage is much higher the sharper the turn. |
agreed.
A solid shaft requires an intelligent operator, that actively engages the front diff only in conditions where wheel slippage is possible, and disengages in conditions that cause the drivetrain to bind because the wheels cannot slip.
A VC is able to slip in a turn, and a VC can also slip when tires are on solid traction surface. The VC generally does not transfer much power to the front diff unless the rear wheels spin, so a VC equipped Syncro is most of the time acting like a decoupled solid shaft equipped Syncro.
imo a solid shaft can work in snow, IF the operator is selective and actively participates in decoupling on solid pavement, and in hairpin turns and driveways…
Basically the operator has to act like the VC, and only engage front diff in anticipation of when rear wheels would be spinning.
I would not couple a solid shaft at freeway speeds unless the snow was very soft and fresh. Otherwise if the snow is firm, the van will skate more when coupled. _________________ My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco |
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IdahoDoug Samba Member
Joined: June 12, 2010 Posts: 10252 Location: N. Idaho
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Posted: Wed Nov 26, 2014 12:59 am Post subject: |
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Soap,
Your question is not unique to Vanagons, and I'm surprised by the comments that the vehicle runs fine on snowy roads with essentially a locked center differential (locked VC or solid shaft with decoupler coupled).
I have two vehicles with locking center diffs that when engaged allow me to compare how they behave on snowy conditions versus unlocked. No way would I say they are fine on snowy roads. On a snowy curve, they are completely unstable and I have to drive SLOWER than if unlocked. At any kind of speed, you are definitely running wide and the vehicle changes attitude constantly as you run on and off road surfaces with more traction, less traction and bare spots. By contrast, when unlocked these same curves at the same speeds are uneventful.
This is simply because the front axles on a curve are describing longer arcs on average than the rears, so there MUST be a speed differential between the front and rear differentials. Lock them, and you have two tires always slipping as one end or the other loses the battle vs the other axle. This is simple geometry.
When you are turning sharper slow speed corners such as when entering a parking lot, or turning at an intersection the slippage is far worse, simply because the % of slippage is much higher the sharper the turn. Under come conditions, you will be turning a corner and suddenly find your turning circle is MUCH larger and you may slide into traffic in the other lane. I don't recommend a solid shaft for operating a Syncro in 4WD on snowy roads. Trails, sure. But there are huge compromises on the road to your safety.
That is my experience using Michelin Arctic Alpin 4X4s, siped Dunlop Radial Rover RVs with studs, siped Safari DTRs with studs, and Michelin X-Ice tires. There is no way to avoid or counter that slippage - it is due to geometry of the various tires paths on a curve.
When someone simply says "It's fine" I have to wonder what their personal definition is. _________________ 1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader |
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soap0007 Samba Member
Joined: August 16, 2011 Posts: 18
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Posted: Tue Nov 25, 2014 10:42 pm Post subject: syncro solid shaft |
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sweet thanks for the info wanted to know before i install the solid shaft ive read that there not good on the road but most of the people saying that live where they dont drive in snow conditions |
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1vw4x4 Banned
Joined: June 22, 2005 Posts: 472 Location: Pgh. PA
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Posted: Tue Nov 25, 2014 10:29 pm Post subject: Re: syncro winter highway driving |
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I do by default. My VC locked solid years ago. I mean really solid.
The Syncro ends up having the exact feel as a old 4x4 truck, or old jeep. Kind of slows down around bends, becasue of front to back axles binding.
Not complains.
soap0007 wrote: |
looking for someone that has a solid shaft syncro with a decoupler that drives it on the highway in winter driving conditions wondering how well it works or doesnt thx |
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squeegee_boy Samba Member
Joined: April 27, 2008 Posts: 762 Location: Langley, BC, Canada
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Posted: Tue Nov 25, 2014 10:20 pm Post subject: Re: syncro winter highway driving |
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soap0007 wrote: |
looking for someone that has a solid shaft syncro with a decoupler that drives it on the highway in winter driving conditions wondering how well it works or doesnt thx |
I do, and I've run it with Nokian Hakkapeliita CS, BFG AT/TA and Nokian WRC Van tires. No complaints. I've never been stuck in the snow anywhere with any of those combinations.
Robyn _________________ 1984 FrankenSyncro Westy. EJ25 RMW kit
1971 Super Beetle with an EJ22. Oh yes. Daily driver |
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soap0007 Samba Member
Joined: August 16, 2011 Posts: 18
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Posted: Tue Nov 25, 2014 10:10 pm Post subject: Syncro Chat: VC's, solid shafts, decouplers, AWD/4WD, etc. |
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looking for someone that has a solid shaft syncro with a decoupler that drives it on the highway in winter driving conditions wondering how well it works or doesnt thx
Moderator edits:
1) Title changed to reflect the course of discussion since it is no longer winter driving-specific.
2) Additional discussion about VC's, 4WD/AWD can be found here: http://www.thesamba.com/vw/forum/viewtopic.php?t=624135 .
3) Winter driving tips & tricks posts have been split off into their own thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=624647 . |
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