Decoupler options

[markswagen]

My syncro transmission took a shit but that means I can now throw some goodies at it, I have a locking diff for it now, a decoupler is the next bit on the wish list.
There are 3 options I know of
RMW $995, I think.
GoWesty $861
AA transmission $895

Please I want to hear pros and cons for each one, from actual experience with them, anything I need to be for warned about.

Thank you in advance.
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markswagen {mobile mechanic} san diego area all early VW's cared for.

619 201 0310

[Waldi]

Is one of these from Lars Neuffer ?
I would take that.

[0to60in6min]

there are 2 kinds - one has needle bearing and the other one has bushing...

whatever you pick make sure it's needle bearing...

[Sodo]

[photogdave]

Syncro Shop in Oregon.
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89 Syncro GL Westfalia 2.1 WBX/WBXaustSS

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[RGS Paul]

I don't like the ones that rely on the spline fitting to be the couple/decouple interface. The German style with the gear style hookup is much faster and more robust, I think AA's is this way. I got mine from Florian in CO back in the day and love it, my Dad has the spline version from GoWesty and he is always nervous about the splines and jealous of how easily mine couples and decouples.

Paul
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'87 Syncro 7-Pass. Adventure Touring Vehicle
"Simplicate, then add lightness." Colin Chapman

[mackaymanx]

I got the AA Transaxle which is the German style. The decoupler is quite good but the bearing was a Nachi 6206 which was sloppy in the clearances. Original bearing was a Styer 6206 p6 which has reduced clearance over a normal bearing. I was having vibration issues and replacing this bearing reduced my vibration problems but did not solve it. I used a SKF Explorer Series bearing which have a p6 tolerance in that size range. Also circlip was reused from a decoupler which had spun a bearing, it had been flipped over to it's 'good' side but should have been replaced. Also had axial runout on the output flange (only about 0.1mm) as the spline was eccentric to the bearing surface, does not help when you are chasing down a vibration issue. Flange runs perfect with the original Styer shaft.
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[url=http://www.vw-mplate.com/mplate2-18600.png]Click to view image[/URL]

[pjn_wyo]

Ask your transmission rebuilder which one they recommend.

They will likely have an opinion.

[Sodo]

I took a long hard look at decouplers a few years ago, then bought one.
I feel like I understand them very well at this point.
My personal "use" for a decoupler is:

Decoupled makes the van easier to steer in tight city driving and parking.
Option to drive the van with mis-matched tires in some emergency.
Option to tow the van with 2 wheels on the ground in some emergency.
Decouple if the Viscous Coupler ever fails "stuck" or hardens.

Driving the van all other times, I'm coupled, in "Syncro"
AWD and the Viscous coupler is what makes the Syncro drive like a dream.
Its why we pay the Syncro tax.

SyncroShop designed (and manufactures) the decoupler for RMW Rocky Mountain Westy. Since appx y2000.

^^Here's a cutaway diagram of the Syncro decoupler on the left <----- AND the "normal" nosecone on the right -------->.

The Bearing (needle, composite, or nothing)

I found that the needle bearing is highly valued by purchasers, then found that it was almost completely unnecessary in use. The RMW unit has a composite bearing, which their salesman (back in Van Cafe Santa Cruz) called "plastic". It's not "plastic", it's a composite transmission bearing, designed to carry load. And it's way way overkill, just like the needle bearing is. And the GoWesty decoupler has no bearing at all - and a solid track record of zero problems.

What does this bearing do for you? There is NO LOAD on this shaft where it goes into the bearing. It simply maintains alignment, it's "a hole for a shaft". The Needle bearing and the composite bearing (as power transmission bearings) are designed to support rotation under load. There is no load. They are both overkill to the max.
But what's wrong with overkill, when bearings are so inexpensive?
Nothing wrong, they're fine. But there's no point in discussing which overkill is better when the usage doesn't stress, thus cannot ever wear out either unit, EVER.

But the Composite bearing has a couple possible possible benefits. The composite has tighter tolerances than the needle bearing (less slop). Needle bearings are "loose", because they have to be. So if you are battling vibrations, a tighter-held shaft is one less contributor. And there's the bigger ball-bearing too, the 6206. VW uses a 6206 "C3" bearing in the OEM nosecone. They cost about $6. SyncroShop uses the tighter 6206 "C2 spec" bearing (which costs $30). Consequently the SyncroShop decoupler shaft, is even tighter held than the OEM nosecone, at each end.

And the needle bearing cannot drain, so when you change your oil to get the pollutants and metal dust out, the needle bearing always holds some old oil, while the composite does not.

The AA uses the normal OEM style 6206 "C3" bearing (and its needle bearing).

OK that's bearings.

And the GoWesty non-bearing unit works fine too, but we haven't heard of someone towing, de-coupled (in 2WD) at speed, with a GoWesty unit.
People flatbed their Syncros.
But I'd say, if you were going to Mexico or something.....and want the OPTION to be towed with 2 wheels on the ground a few hundred miles,,,,,I'd prefer one with a bearing. With that GoWesty unit, if you had to tow decoupled for a long tow, prob should tow ass-end up so the nosecone is flooded with oil. Cuz the shaft will be spinning at 4,000 rpm in that hole (but with zero side-load). Again, no worries, if it's flooded with gear oil by "ass-end up". Keep in mind your differential spiders are built like this (no bearing) and they never wear out. They withstand huge side-loads but are not subjected to 4,000 RPM (no-load).

The Coupling (Heavy-duty coupler, or simple spline coupler)

Then the other difference is the "coupling" style. GoWesty and RMW slide a coupler over splines, and the AA and some German units have a huge coupler tough enough to use in the main forward speeds, able to withstand RPM mismatch of constant gearshifting like gears 1-4, shifting all day long, for the life of the vehicle. Thousands and thousands of mismatched RPM gearshifts, some of them ham-fisted. The decoupler however, shifts 5x per year, when a gentler little vacuum decoupler is "able" to move the coupler ( a no-load condition between the two shafts ). On many Syncros it shifts only to verify that the dash light comes on.

^^Here's a pic of the AA coupler unit and the large external engagement teeth. And you can see the needle bearing too.

^^Here's a pic of an old-style Syncroshop decoupler that engages/disengages the splines. These spline-engagement decouplers have been in-use for over 15 years and there are no reports of any spline wear.

The oversized external engagement was a solution to a problem that never existed. Not a bad thing, just not necessary.

The decoupler shifts ONLY when the little vacuum actuator is capable of sliding the coupler. ONLY when the two shafts (front diff & rear diff) are rotating exactly the same speed and "unloaded" can the coupler slide. It's the gentlest shift you can ever imagine. What POSSIBLE reason could there be for a big expensive heavy-duty coupler? Here it is: It's "marketing" to people who do not understand how gentle the "shift" is. If theres any mismatch in shaft speeds, the little blue vacuum actuator just can't do anything. It has to wait for a lull, then it gently moves the coupler.

So when decouplers cost the same it kinda comes down to, what feature do you want the money spent on? Nice shifter mechanism with a simpler coupler unit? Or heavy-duty coupler and a cheap shifter? I prefer the nicer shift mechanism.

Here's some technical discussion on: Are all decouplers the same? with photos
and a decoupler cutaway diagram.

^^ Above is a pic of the "old style" shift-mechanism on the RMW decoupler. Its from a few years ago.

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

^^ Here's a pic of the new style since appx ~2015.
Its a normal shift fork like the others (not de-spun on bearings) Look at the little nubs on the shift fork. The spline collar and shift fork are 4140 steel. Beautiful stuff, CNC components worthy of an $8,000 transaxle.

Well anyway I hope this info helps.
The funny thing is -- what difference will it make between all 3 units?
Not much.
I'd be real surprised if there was any difference between the units in operation. they ALL have to wait for the driveline to relax tension, because all they have is that little blue actuator pushing on the coupler.
No need to be nervous about the splines, it's a gentle shift.

My AA decoupler had a failure because I am jinxed.
I don't hear other decoupler failures, any.
And BTW Matt at AA recently refunded my $1395, and sent me a complete set of new transaxle bearings for my (next) rebuild; as an apology for the (2015) decoupler failure. It just took a few years. He also said now they press the shaft into the shift fork, plus an e-clip.
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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

[markswagen]

Thank you Mr sodo, that was quite the read.
Now I'm leaning towards the RMW decoupler.

Drat, yesterday the purchase of a switch panel fell through, after I'd paid for it in Germany, the seller found that someone else had sold it.
Dave, please don't edit this, I am NOT !!!! asking the masses to help me find one, just a moments frustrated venting.
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markswagen {mobile mechanic} san diego area all early VW's cared for.

619 201 0310

[PNE Syncro]

My opinion on de-couplers is unless your running a solid shaft on the front Diff instead of Viscous coupling I think the $$ would be better spent on a Peloquin Diff or HD gear Housing. I bought my decoupler from Dina the German many years back, It has a needle bearing pilot guide and that is the only guide I would want on my de-coupler unit. VW actually never did offer a de-coupler and its MPG differences arent enough to offset the "Price of Admission" in my book. 3 Knobs do look COOL!

[crazyvwvanman]

I don't know how many they may have actually produced or sold but the various parts of the factory decoupler are clearly shown, with part numbers, in the VW Parts Illustrations for the Syncro transmission.

EDIT:
the VW Parts info shows it only in transmission code 6ZA
tranny code 6ZA shown produced 2/85 to 7/87

Mark

[ALIKA T3]

[Waldi]

This mpg proofs are worthless.

[markswagen]

I'm not interested in gas mileage, so let's please keep that out of it, currently I don't have the drive shaft to the front diff is standing up in the corner of my garage, another job for another day, I belive it's got a split rubber joint on it.
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markswagen {mobile mechanic} san diego area all early VW's cared for.

619 201 0310