Hi All-

I have a 2000 JGC v8, with 66k miles. When Im driving down the highway
my rpm jumps from 2000 to 2500 then back down and the speed does not go up. Speed is roughly 70mph and it happens about every 10 seconds or so. Happens when in cruise as well. It does not happen below 2000 rmps going roughly 60. Any idea whats causing this?

It sounds like the torque converter is unlocking.
Check the transmission fluid level.
Tapping on the brake pedal at speed will manually unlock the torque converter.
If this replicates the symptoms, it is likely is the transmission.

Thanks for the response. I drove out on the highway to try the tapping but everything was fine. Rpm wasnt jumping up and it stayed at 2k like it should. Hopefully a fluke thing. Tranny's are pretty expensive for these.....