Date: Sun, 15 May 2005 22:04:27 -0400
Reply-To: Kim Brennan <kimbrennan@MAC.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Kim Brennan <kimbrennan@MAC.COM>
Subject: Re: Need Viscous Coupling Refresher Course - '91 Syncro
In-Reply-To: <9d6421950505151803588941a9@mail.gmail.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed
In normal driving (and certainly highway driving), you will NOT want to
lock the rear differential (or front if you have one). The differential
allows for your wheels to turn at different speeds, this is very nice
when making a turn. The time when you WANT to lock the rear
differential is when you have (or have the potential to have) both of
your wheels spinning, such as in snow, ice or mud. In other words, you
only lock them when you really need to and unlock them as soon as
possible.
The differential lock is activiated by a vacuum switch, so if you have
a leak in the vacuum line it is possible that you won't see the
differential lock. Note, locking is NOT instantaneous. It does take a
revolution or two of your wheels before it engages.
The nature of the Syncro mechanism is such that you can get stuck with
spinning wheels, if ONE of the rear wheels is spinning and ONE of the
front wheels is spinning (rear diff lock not engaged.) If the rear diff
lock >IS< engaged, then you can get stuck with ONE of the front wheels
spinning and BOTH of the rear wheels spinning.
On May 15, 2005, at 9:03 PM, vanagon teepee wrote:
> Hi All,
>
> I have some very basic questions about the viscous coupling and the
> best 4WD practices/ operation for my '91 Syncro Camper. I used to
> know some of this stuff, but it's been a while and now I only know
> enough to ask the questions. :-)
>
> 1) Is it accurate to call the Syncro an "on demand" 4 wheel drive or
> All Wheel Drive? It's my understanding that the viscous coupling is,
> in effect "always on"..with the discs always spinning and ready to
> transfer power instantly to the wheels with traction. Is that
> accurate?
>
> 2) Is it nonetheless possible for my viscous coupling to somehow be
> broken or not functioning? I was testing it recently starting from a
> stop going up a steep slippery road, and I got the rear tires spinning
> nicely but with no obvious, notable help from the front tires kicking
> in. (I am not 100% certain about this...they may have a little.)
>
> 3) When I pull out the differential lock knob, nothing happens...no
> light, no lock that I can tell -- nothing. What's the likely cause?
>
> 4) Under most circumstances where you would want the 4WD to actively
> kick in whenever needed (driving in snow for example) is it still
> better to keep the differential unlocked?
>
> What ARE situations where locking the differential makes a big
> difference.?
>
> Thank you.
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