Cruise control & TCL

When I use the cruise control on my 99 4x4, 3.8L with Auto, the Torque converter lockup cuts out and in while going on the level. There does not seem to be any throttle activity at the time. The lockup works fine when not using the cruise control. The cruise seems to work fine at holding the speed. Any ideas?? Both me and my neighbor who is a Dodge mechanic are stumped without spending a ton of money to find out.

Any help appreciated.

CPeter