It is a mechanical system, using vacuum pressure to move the locking
parts in and out. No electricals are needed to operate the lock. There
are some simple electricals used but these are only to light a bulb on
the dash whenever the locking mechanism is engaged.

A vacuum line runs from the engine intake to the dash. There it connects
to a vacuum switch. The switch has 2 positions. It has 3 vacuum line
connections. One is vacuum in, the other 2 are vacuum out. In 1 position
vacumm is present on one of the outputs, in the other position it is
present on the other output. 2 lines go from these switch outputs back
to the tranny.

At the tranny, a vacuum actuator is bolted on to a bracket and attached
to the locker shaft that comes out of the side of the tranny case. The
vacuum actuator has 2 places for vacuum lines to plug on. When 1 of
these has vacuum, the actuator pushed the locker shaft into the tranny.
When the other has vacuum it pulls the locker shaft out from the tranny
(unlocked).

On the tranny case above the locker shaft is an electrical switch that
is operated by the locker parts moving within the tranny. Wires go from
this switch to the dash where a light comes on the tell the driver that
the locker is engaged.

The vacuum source is the engine intake. It is spliced from the vacuum
line to the brake servo to a vacuum reservoir and then to the dash
mounted vacuum switch.

Mark

Jeff K wrote:
>
> thanks for the replies regarding the locking diff in the 2wd. Lots of people interested, but it doesn't look like anyones done it. Darrell at AA says he'll do it for $500 over the price of a rebuild; Weddle is something like $400, but their rebuild is 1200. In either case, you have to buy the locker servo and all the other stuff seperately.
>
> Can anyone explain to me how the locking servo works, and what other parts I'll need? I looked in the Bentley, it was kinda vague. I'm assuming It's a vacuum lock, meaning I'll have to run vacuum lines from the engine to the tranny and back. Do I need a vacuum tank, too? And then some kind of servo to control the vacuum, with associated electrics running up to the dash and back? I've never seen one on a van, so the more details the better. thanks again.
>
>  Jeff
> Bisbee, AZ