help: locked diff on a 84 4KSQ

["Alnis, LLC" <zmsllc@ix.netcom.com>]

Hi, I asked about stereo removal last week and got some good advice on that,
but before I go there, I had a disquieting weekend with my 84 4000sQ.  Late
friday night, all of a sudden it looks like one of the differentials is
locked.  Here is what happened:  Things felt normal driving on the freeway,
and I didn't have to turn at all for the first mile or so off the freeway
(Fell St in San Francisco for the curious.)  Then when I made a normal
right turn, the car bucked and shuddered, like the brakes were dragging or
something.  It was normal on the straight, but funny on left or right turns
thereafter.  I managed to park it and tomorrow morning I plan to drive it
to a mechanic for an estimate, but I would love some advice first :-)  I
was busy this weekend and had to time to do any investigation, in fact I
didn't even think of the
diffs for a while.  I was stumped as to what else in the drivetrain or
brakes could bind up only in turns though!  So tonight I plan to at least
jack up
one rear wheel and see if I can till if the center diff or the rear diff
is locked.

Since I've owned the car (94), I'm not sure the vacuum system has been
working to engage the diffs.  Occasionally, when I was on a dirt road, I'd
pull the knob out to the first or second stop.  Sloooooowlly the light for
the first diff (center?) would flicker and  eventually go solid, but the
light for the second one (rear??) would not. And it didn't feel any
different driving, although until now I don't think I realized how dramatic
an effect it can be!  Then about a year ago, the light for the center diff
started coming on all the time, but again, the car felt pretty normal to
drive,
even at low speed, hard steering turns.  The light went off for a few
months recently after the tranny and diff. oil was changed, but then
started flickering on again like it used to.  I don't know how pertinent
this is to my current problem, but it seems like it could help.

If anyone has some advice I'd appreciate it!  What could be wrong, how
expensive to fix etc. The car has 140K miles, seemed in fair condition at
best before this particular problem.  I've recently had the  brakes done,
timing belt & lifters replaced and general service stuff done by Ed Novak
in SF (where it is headed tomorrow)

thanks,

-Mike Perrott
zmsllc@ix.netcom.com