[urq] Diff lock mods?

Louis-Alain Richard laraa at sympatico.ca
Wed Oct 25 11:42:21 EDT 2006

> Has anyone modified the URQ diff lock set up to be manual as opposed
> vacuum operated?
> On my late build 83 (now totaled) the locks worked but were quite
slow, and
> had the ability to lock center only or both center & rear. My current
> build 83 has an "on off" set-up linking both center and rear, and will
> them but not disengage them.
> Over the weekend I had the car up off all 4s and used a vacuum pump to
> thoroughly test the system for leaks, and both the green (engage) and
> (disengage) systems are leak free. The red system just doesn't have
> grunt  to
> pull the diffs off.
> I would like to go to a manual system with levers and control cables
> need to source some "custom" parts and cables, and was curious if
anyone else
> has already done this.
> Dennis
> Denver

Dennis, I had the same "laziness" problem on mine but I managed to help
it without redesigning the whole system. 

- front diff lock: I hooked a 6" long spring to the Bowden Cable to help
the return function. The other end of the spring is attached to the fuel
pump bracket with an adjustable length wire in parallel to the Bowden
cable itself. This way, I can tension the spring just enough to let the
green system pull against it. Now, engagement is OK, but disengagement
is immediate.

- rear diff: this one shouldn't need help because there is no internal
spring to overcome (as in the front diff). If it is slow/hard to rotate,
then it must be friction (rust, grime, wear, etc.) or maybe the little
pin is rusted in the fork/lever assembly. I replaced it with a stainless
steel bolt, and greased it thoroughly. 

Another data point: when the rear diff locks but doesn't unlock, it
usually means that the little rubber boot on the rod is leaking. The
diaphragm is often OK. For the front diff, it is the opposite; if the
rubber boot is leaking, then there is no engagement.

Another possible problem is from the check valve ahead of the switch, on
the white vacuum line. If it leaks, each time you push into the boost
(which should be OFTEN...), you create havoc in the locking systems...

Finally, where did you test the vacuum operation ? From the switch in
the dashboard I guess, because testing just the actuators won't reveal a
leak in the tubes, but I am sure you know that...

Good luck !


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