Torque Converter Unlocks Momentarily

[hbelt]

I got a 1998 Chevy Silverado 5.7 with 4L60E tranny. It started giving this random issue after driving for about 30 minutes. Its when it's in overdrive with the torque converter locked, and often when cresting a slight hill and slowly backing off the the gas, it will do this hiccup, like the torque converter unlocks and locks right back up again. like I said, it only does it when it's good and warm. Any advice as to what the culprit is would be helpful.

 

[Schurkey]

The converter is set up to unlock when under light throttle (coasting). Totally normal. Irritating, but normal.

 

[hbelt]

Ok, I just didn't think it should jerk the whole truck like it does. I had a '97 and that one didn't do it. I suppose maybe something is worn that makes it jerk more than normal. The truck does have 260,000 miles on it.