Decouplers

41

I had a decoupler installed. I would recommend it  for all syncros. Because of their age, it is quite possible that the VC is not quite as good as new, or the front diff may have an issue (or starting to develop one) and the same for the side shafts and or the alignment. So on tarmac, I have AWD is disengaged and as soon as I hit the dirt, I engage AWD. This is done on the fly although you use the clutch with engaging and disengaging.

 

To decoupler also helps on tarmac if your front to rear tyres are not equally worn. Unevenly worn tyres place no strain on the drive train off road, as there is constant wheelspin to absorb any buildup of strain.

 

Before fitting the decoupler, I experimented extensively by removing the propshaft but there was not material difference in fuel consumption. Therefor should you experience an improvement in fuel consumption by removing the propshaft, it may indicate that the VC, front diff, side shafts or alignment is not well, thereby causing additional strain on the drivetrain.

 

The syncro gearbox is essentially based on the 2WD 2,1i gearbox and for this reason I can not understand why running in 2WD as opposed to 4WD would create greater strain on the gearbox.

 

Perhaps your experience is different.

 

Regards,

 

Piet Coetsee

 

Managing Director

 

 

 

T: 021 910 2654

F: 086 20 20 204

E: piet@smartpropertyservices.co.za

W: www.smartpropertyservices.co.za

 

 

From: Syncro_T3_Australia@yahoogroups.com <Syncro_T3_Australia@yahoogroups.com>
Sent: Saturday, 06 October 2018 10:27 AM
To: Syncro_T3_Australia@yahoogroups.com
Subject: Re: [Syncro_T3_Australia] Decouplers

 

 

Gaetan,

Consider also that there could be worn universal joints in the prop shaft plus and the angles on the drive shaft faces may be incorrect.

Ideal - aim for 4 degrees down at each face - or more, make both faces the same angle.

It's an interesting fact of physics on the way in which the input shaft can turn less or more then the output shaft if the angles are different. 

watch this

 

42
Hi!

thanks for that info, I’m going to look into this 4 degrees thing.

FYI I have just had the prop shaft serviced recently - it’s had brand new proper VW u-joints both ends and was balanced.

It’s kind of hard telling where the noise came from while driving - I had my gf drive with me hanging my head out of the window and sliding door and I could have sworn it came from the rear on the right hand side.

With the van jacked up though, both rear wheels spin freely by hand, and after removing prop shaft I ran it with rear wheels in the air - no prob, then on the road up to freeway speeds in 2WD, no prob.

A bit stumped for now..

Gaetan

Sent from my iNuke
43
That was a really cool driveshaft video by the way.

Now, how do you measure and adjust the angle of the faces our prop shaft mates to?
Also, when my shaft was serviced, they resprayed it in black so it has no marks. I thought since it was freshly balanced it would not matter, but having watched that video there’s obviously more to it. Plus the fact it was vibrating pretty badly when I got the van, so no idea how long for or how much damage that may have done, or where.

And I need to check out my gearbox - or at least the selection mechanism - as it has a tendency of not staying in 1st gear when idling at the lights, and also pops out of 4th every now and then while driving.

Sent from my iPad
44
I don't think that there would be any difference in gearbox wear but the ring and pinion would be under less load as the power is split over 2 axles. This is why the Range Rover had permanent 4WD,
45
I doubt if there is a viscous coupling that is still working to factory spec after thirty years. I threw mine out years ago and replaced it with a solid shaft and decoupler, now I can engage four-wheel drive before I need it, not wait for the rear wheels to lose traction before the VC engages.

The VC was originally designed for inexperienced drivers ferrying vanloads of kids safely to school through snow and ice in the Bavarian Alps, not for gung-ho off-road heroics.

Most transmission breakages occur through the application of a heavy right foot. Wheel-spin followed by sudden grip transmits enormous shock through a transmission designed for a 68 horsepower 1700 kombi 2WD back in 1974 - without the torque multiplication of Gelande gear.

With skilful wheel placement and delicate throttle control you can drive around the stranded heroes without busting anything, and your van will last a long time.

My trannie is still going strong.

(Spoken by a true hypocrite who just bogged his rangie up to the doorhandles because he was to lazy to walk through a shallow-looking puddle first)!!

Dooh.
46
Hey Roger and all, don't know about factory spec, but my visco works well . I know it's original because apart from Telecom, I'm the only owner. Done about 700 thousand KMs , pulls tight U turns and gives drive to the front when needed. Maybe the country Kay's, same size tyres and being driven daily might be factors in its longevity. Eddie.
47
Gaetan
Hi there
First off you need to check that the gearbox (transaxle ) and engine centre line are inline with the front diff.
Use a string line to do this.
Adjust to achieve straight line.

Then with the drive shaft removed measure the vertical angle at each drive flange.
I see smart phones have an application for measuring angles - use this.
Ideally you should see 4 Degrees ( minimum ) down at each flange.
 Make both flanges the same angle.
Use washers under the mounting flanges on transaxle or front differential  to achieve this.
Also consider replacing all mounts.
Chris at http://www.t3technique.com/ carries these bad boys
Van cafe carry the hard plastic washers


Have fun.
Peter

48
More interesting reading! The tail shaft does seem to be a source of a lot of issues in Syncro's

In relation to the fuel consumption, I have not noticed any difference running with the tail shaft in or removed over many km. I know this contradicts the articles mentioned, but the difference (3% noted in one) would not be noticeable in normal day to day driving.

The load on the GB is an interesting one, from my experience the GB in a stock 2WD T3 easily outlasts that in a Syncro, and that includes a (2WD) single cab that spent much of it's life heavily loaded or towing. So there must be a difference in design, be it a weaker case or some additional loads in the Syncro. I also have always used less fuel in 2WD T3's.  The spreading of load in a constant 4WD makes sense (ref note about range rover) if you have an open diff between the front and rear axles. By design an open diff applies the same torque to each side, so yes will split input torque evenly to all 4 wheels. I don't see how this applies to a VC (or solid shaft) which by design maintain constant speed to each side (not torque).

The video on the tail shaft angles was a great visual representation of what is happening in the drive line!

Richard