I had 600HP built 700R4 and boss hog 2800 stall converter put into my car.

I noticed in second and third gear when at cruising speeds, if you punched the throttle when the engine was running below the stall speed, the engine would jump to 4k then immidiately fall back down to 3k and grab.

I thought it was tranny slip at first but I called and talked to the torque converter company and they said it is because the engine is being revved below the stall speed and the converter has to play catch up. It sounded feasable since this does not occur if the throttle is punched when the engine is at or above stall speed. I just wanted to see what everyone else here thought.

Something sounds wrong. Going full throttle should cause a downshift, which should get your engine rpm high enough. Does your combo retain converter lockup? If so, is the converter locking up when cruising?

Also, you need a 3.73:1 axle for a 2800 converter. I have plenty of experience with too-tall gearing with too-loose converters.

I was holding third gear the whole time and not allowing the trans to go into overdrive, so there was nothing to downshift to. Also, I didn't do WOT. I gave it about 3/5 throttle and my rear gears are 3.23.

How do I verify that the converter is locked?