I get the same "fish Bite" only when cold. (5.3 6sp tran). Goes away usually within .5 to 1 mile (in Florida where temp are a lot warmer then north)
My dealer tech rep told me, that the transmission has a thermostat in it, and until it warm up will cause that issue.
If they know the issue, why cant they just replace the thermostat, if replaceable. I know for instance some transmissions on some vehicles are so complicated that the manufacture will not allow the dealer service techs even open up a tranny.
These stupid things they put into vehicles cost us more, create issues, all for a sill "presumed savings" in fuel. IE Auto Stop Start, V8-V4 crap.