Differential Locking Problem '88 5KCSTQ

[choate@leland.stanford.edu (Keith Choate)]

Hello All,
   I've been having a problem recently with my front and rear differentials
locking spontaneously (with the selector switch off) at high speed.  This
seems to happen more often in fourth and fifth gear when turbo boost
exceeds 1.1 bar (60+ mph).  As soon as the turbo passes 1.1 bar, I hear the
ABS relay switch kick in and the rear, then front, differential indicators
light and the ABS turns off.  As far as I know, the differential lock
indicators only light when the differential actually engages.  Since the
differential has luckily only kicked in on straight stretches of road, I
have not determined if handling is reduced and I can not confirm that the
differentials are actually locked.
   Has anyone else ever had this problem or do you know what might be
causing it?  It sure has me stumped.  Any suggestions would be greatly
appreciated.

                                                        Keith Choate