Syncro 4&4 Discussion and Q&A last answered over 2 years ago.
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Diff-locks lock the left and right sides together, front and back if you have the separate actuators on your dash (some foreign syncros only have rear)
taking the prop off is the sure fire way of disengaging the permanent four wheel drive and removing the problems associated with aggressive VC's or mis-matched tyres that strain your drive train.
The Speedo will still work as it is driven from the front diff which still turns with the wheels when your driving.
Mine has also 2 knobs so front and rear difflocks... the thing is I am going to install a decoupler because I don't like VC, and only because you don't know when a VC stops of working, when a VC doesn't work correctly, can ruin the gearbox and that is not cheap...
Victor Diaz
'86 Syncro 14" Westfalia Canary Islands
true enough a dodgy vc will wreck your gearbox but before I'd go looking at buying a decoupler might want to look consider other points of veiw in favour of the the vc versus solid shaft??
I can get a decoupler for less than 600€ so it is a very nice opportunity... and, anybody who has installed decouplers... a decoupler can ruin your gearbox or 4x4 system?
Victor Diaz
'86 Syncro 14" Westfalia Canary Islands
From my understanding; 1) you either run with the VC, 2) run with the VC but with a decupler or 3) run with a solid shaft and a decoupler.
1) If your VC goes very tight you risk transmission damage and suffer the tight turns issue often discussed. But you have permanent 4wd on all surfaces.
2 You continue with your tight VC as it is working well when you want it (off-road) but you put in a decoupler so you can switch it into 2wd when not required; no risk of transmission damage, but you can put your VC into use on road if conditions require it.
3) You remove the VC insert a shaft in its place and install a decoupler. You never have 4wd on tarmac/paved roads but have a true locked 4wd for off-road use when its required. This is more effective than the VC in most cases as drive is immediate. But you lose the advantage of the permanent 4wd at any time on the road.
So always a pro for a con or a horse for a course!
I went for option 2. A de-coupler and sports visco (as fitted to 16" syncro's) or it might just be tight??. Works very well. Parking and turning is now so much better. You can engage or disengage at any speed, just need to lift off the throttle momentarily.