Recently, my 98 Durango with 360, auto, 4x4 started revving up by 200 rpm's
instantly when on the interstate or pretty much any other speed as long as
the cruise control was on.  I first thought the transmission was slipping
since when the engine revved up so quickly the forward momentum of the
vehicle seemed to stop.  Just like when the engine revved up the
transmission would instantly go into neutral.  This intermittent problem
would end as quickly as it happened and then start again.  Like every 30
seconds it would happen and then other times it would go for minutes without
doing it..  You could just tell by the tachometer and the loss of forward
momentun when it happened..  It does not exhibit any problem as long as I
manually control the accelerator.  So is some sensor going bad somewhere or
how can this be fixed?  There's around 90k miles on this completely stock
Durango if that matters.

Ben in TN