Syncro Drive Shaft Decouplers

[Howesight]

Back when I had Darryl Christiansen (RIP) rebuild and regear my Syncro transaxle for the SVX engine swap, I was seriously considering the solid-shaft approach. Darryl talked me out of that and suggested a "sport" VC. My VC was quite tight already (always squealing the tires on pavement when doing tight turns) so I stuck with the VC approach. I agree with livethevanlife above and strongly suggest staying with the VC approach. Our rig has the decoupler, rear diff lock and front diff lock. It literally goes anywhere. Decoupling allows some flexibility in town and when making repairs or doing maintenance.

My original thoughts about using a solid shaft in place of the VC were based on my experiences with Toyota 4x4 vehicles, 33" tires, and the ultra-low gearing available in "Low-4". With a rear diff lock on the Toyota, I could literally crawl up rough slopes until I got some tire slip and then had to resort to using intertia (AKA taking a run at it).

Realistically, this approach is simply not available with the Vanagon Syncro because we can't run 33" tires (or 35"s for that matter) and because the (Gelander) granny gear is simply not a low enough ratio to permit that kind of crawling. So, a bit of rear wheel slip before the VC fully engages is acceptable to me and a reasonable compromise when compared with having to decouple when not on a loose surface. The drivelines in the Toyotas can easily withstand the windup that occurs in a 4WD setup, but in a $yncro, that approach gets ex$pensive.
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'86 Syncro Westy SVX

[pindrums]

Good info on the VC's & decoupler stuff. I anticipate a lot of highway & medium speed dirt road driving with little (serious) off-roading - therefore my questions. I had no problems with the stock VC & single knob in my last Syncro (vehicle completely burnt up in 2019!) but was curious about upgrading to a de-coupler in this one I just bought.

[silversync]

There is one additional advantage for a decoupler, and that is using a smaller spare tire that fits in the clamshell. I think most Syncro owners upgrade their wheels and tires to larger sizes. And then buy a 5th set and a tire rack for the rear. With a decoupler it is possible to use one of the older 14 inch wheels / tires that fits in the clamshell. The means saving the cost of a large wheel / tire and the rear spare mounting rack, probably $1K or more (pays for the decoupler). For me since I use the Syncro often / daily I don't have to be parking lots and swing that tire rack out of the way just to open the hatch to load the groceries.

There is one additional advantage of the straight shaft. It doesn't fail. The VC can fail open without notice and then you'll be stuck without any front wheel drive at all. Yup, my VC failed without knowing when it failed, and then discovered that while off road.
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Roland: '89 Syncro, '02 911 C4S, '10 Audi A4 Avant

[Sodo]

[pindrums]

Well, my previous Syncro (which burnt up) had "big" 14" tires (I forget the exact size), and I had to buy an aftermarket front fastening kit, plus fabricate rear shackles to lower the clamshell to get my spare to fit. It worked but hung down low and bottomed out occasionally offroad. [Looked stupid too!]. My best option then and now [for me], is putting it up inside, against the left-side wall (right behind the driver's seat). Easy to get to (important!), out of the way (an empty tin top) - the bed opens up fine into it, etc... So, I think I've decided on what to do based on responses here with my original question; now not sure if I should change out the driveshaft or just leave it. It's not giving me any problems. Thanks for all answers!

[Sodo]

[tjet]

[dobryan]

[livethevanlife]

[tjet]

[Sodo]

I like the way the van drives in AWD.
I like that it pulls with two R&Ps, which relieves duty on the rear R&P.
I like the decoupler because I'm a Syncro nut and there's no way on god's green earth I would NOT have one (or at least be on the hunt for one).
I'd go for the VanCafe / Syncroshop unit because it has the tightest tolerance bearings that support the little 4" long stub shaft inside 'the best'.
For the least possible chance of driveshaft vibrations.

WRT Viscous Coupler options....
I'd go for a Sport VC for my style of off-road.
I'd want it to lock up quickly, aggressively.
If I had a sport VC, I would do my 'tight/town' maneuvers slowly whenever possible.
Perhaps decoupling, if I was going to be in town all day.
If you are observant, and understand your AWD system, you can tell when it's binding.
Binding is NOT dangerous. It's just higher loading at that moment.

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When I do quick, tight maneuvers on pavement, I can feel it.
If I do the maneuvers slowly, I cannot feel it; because it's not locking up.

For example:
If I do a tight u-turn, somewhat aggressively because of heavy traffic etc, I can feel it binding up.
Those times I wish I would have decoupled (with 20/20 hindsight).
But you can't decouple during a 'fast move'.

I bet slow, gentle drivers don't stress a VC/drivetrain anyway.

Now.....
if the family member driving this expensive antique fulla NLA parts......
is a teenage male known to drive with reckless abandon.....
that could be different.

===============

If your tight-turn maneuvers are usually gentle, slow, don't worry about it.
If your tight-turn maneuvers are OFTEN abrupt, quick, then decoupling may preserve your Viscous Coupler.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[tjet]

Ok, I just signed up at Van Cafe to notify me when their decouplers are back in stock.

Can you install a decoupler with the transaxle installed? I don't want to hold up my rebuild.

Sodo, would you install a sport VC and no decoupler?

Cheers

[Steve Arndt]

[ALIKA T3]

I doubt the shim under the circlip is for balancing purposes, I mean it does in a way to center the U-joint but the primary purpose must have been there to help having a tight fit with the circlip bc of machining discrepancies.
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Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[MsTaboo]

[Sodo]

[tjet]

Yes very sporty

The breaker bar was a good way to show the resistance