Cherokee torque converter unlocks?
 

`89 Cherokee 4.0L, automatic, about 154,000 miles.

Occasionally at speed the Cherokee lurches and there's a bang from the
drive train. This only happens in warm weather (above 70F or so), at
speeds between 30 to 60, and it _seems_ to happen when backing off
slightly on the gas to feather speed down a point or two. I'm told that
this is the torque converter unlocking and then relocking, but it isn't as
smooth a transition as when it normally locks or unlocks for overdrive,
and doesn't happen at a logical shift point, engine-wise. It happens on
its own, there's nothing that I can do from the driver's seat to force it
to happen, and the position of the power/comfort switch makes no
difference. I've had this Cherokee about 3 years and it has done this
little trick for as long as I've owned it -- but only in warm to hot
weather.

Is this a computer malfunction? I gather from other threads here that the
computer controls the shift to overdrive. And, I have my suspicions about
this computer anyway, as it emits an RF signal that crosses into the FM
radio antenna lead and produces a scream at empty FM channels -- but since
it is an a PIA location behind the dash I'd like to be reasonably sure
that it is actually the problem before I go pulling it out.

Anyone run into this problem before?