Surging RPM's at speed

[LittleBeast]

I replaced the tranny, torque converter, and all solenoids this past summer, and it has been running like a champ. What would cause the torque converter to lock and unlock like that?

[ohiovx]

If that's what is happening, it could be a solenoid going bad, the actual torque converter clutch material wearing out, or the seals for the torque converter clutch piston getting worn & letting the fluid leak past them. Most likely the seals. that would let the piston apply pressure to the clutch,engage, bleed a little, disengage, & so on. It may have also worn the clutch material for the lockup.