Re: TQC differential lock system/ HELP!

[raf40@oes.amdahl.com (Richard Funnell)]

Steve,

>I've got a sort of strange problem here.  The TQC's differential lock
>system is relaly screwed up.  The diffs don't lock, but the indicator
>lights come on sporadically.
>
>
>Anyhow, I can figure all the other stuff, but any ideas on the diff system?
> They say that there's a vacuum leak somewhere (gee, since it's a vacuum
>actuated system, that took lots of brain power), but they can't figure the
>lights ( how 'bout water in the lines causing intermittent pressure/vacuum
>surges that trigger the light switches?) and they say that the center
>differential is shot nad can't be actuated manually.  My bet is that the
>actuator is shot, not the diff, or I would be able to tell that driving.
>Am I right on that??  Steve, Dave, Glen, Scott..???  Of course the big
>question for me is, how can getting flooded mess these things up?
>
>By the way, this '83 has the two position console switch, but the old setup
>on the actuators.
>

I recently had problems with my diff actuators, and I finally bought a hand
vacuum pump with a gauge, and crawled under the car to play with them.
Some thoughts:

-       If your rear diff locked, you would know it I'm sure.  You may not
notice your center diff locking, esp on straight roads.

-       Vacuum surges could only trigger the lights by actually engaging
the diff locks.  The vacuum units lock the diffs, and the light switches
independently sense that has happened.

-       If you ingested water into the vacuum system, you may still have
some in there, and you may have screwed up one or more check valves.  The
locks can get really strange if the check valves don't work, since your
engine goes from vacuum to no vacuum to boost.  I recall one post about the
diff locks self engaging at high speed under boost because of a bad check
valve.

-       You may have a combination of intermittent problems.  I would
suggest using a vacuum pump to individually check the actuators under the
car.  You will see if the one for the center diff can move the cable.  It
is supposed to push the outer cable sheath towards the front of the car @
3/8inch(guess?) to engage the lock.  The rear unit moves a lever and takes
less force.

-       If the vacuum units work, the lights should come on on the stands.
You may have to jiggle the wheels to allow the locks to engage.

Richard Funnell,
San Jose, California
'83 urQ
'87 560 SL