Jeep Cherokee Forum - No throttle response between 40-50 Mph?

I've had an issue with my Cherokee for a few months now where I get little or no throttle response between about 40 and 50 Mph. If I depress the accelerator anything from 1% to 80% I just get bucking and no power increase. If I come off the gas completely the bucking stops.

It feels very similar to trying to drive in too higher gear in a stick shift.

The only way to get through it is to kick down, so the trans downshifts and you can build speed to past 50mph

Then you can allow it to drop back into the higher gear and around 55+ it's absolutely fine.

Any ideas what would cause this? Is it a TPS or a trans issue?