Ford Explorer: 97 Explorer XL clunk and 4WD issues

In the '97 and later versions of Control Trac, when you select either
4WD-Hi or 4WD-Lo the transfer case clutch pack is engaged continuously
to lock the front and rear drive shafts together. This should only be
used in poor traction conditions or going straight ahead as when the
truck turns, the rear wheels go a shorter distance than the front and
since the axles are locked together, something has to give! Either the
wheels drag on the ground or something breaks or pops in the drive
train. Shouldn't be trying that! In 4WD-Auto, the clutch pack in the
transfer case is periodically pulsed to close, allowing drive line
bind-up to be quickly relieved, and that engagement time is regulated by
the GEM looking at the relieve speeds of the front and rear drive
shafts. If the rear is going faster than the front, for example, it must
be slipping so increase the clutch engagement time in 10% increments
until the speeds match or the front is going faster than the rear.

The flashing lights mean "something" is wrong in the automatic system
(usually a bad speed sensor or electrical connection, worst case a bad
GEM or clutch pack), or low range is not getting engaged (bad limit
switch or motor or just stuck). In the failure mode, the 4WD-Auto
reverts to 2WD, only, but I believe you still engage and lock the clutch
pack in the other positions. Sounds like you may have a problem with the
Auto system (which is designed to handle rain and wet streets and such),
but the rest "was" OK. Hopefully nothing vital broke during that
experiment.

=Vic=
Bear Gap, PA

entropy_magnet wrote: 

Vic Klein <net> wrote in news:net:
 
clutch 
the 
such), 

Swung by Aamco yesterday, They pulled the test drove it and pulled the
codes from the transfer case(transfer case needs service and several
failure codes stick in my mind), and said the transfer case was probably
fried, or at the least the motor in it. Not having the 1600 they quoted
me as probable, I took it home and disconnected the battery to reset the
fault states, as well as the 4wd engage command(I suspect). This has
made the symptoms go away for now, though I will be checking sensors/GEM
etc, soonest, and babying the truck until then.

Thank you for the input.

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