Shifting Hard at High Speed

Lately I've noticed that my 97 Tahoe is shifting hard and bucking when going into high gear. This only happens when I accelerate to approx. 55 mph. Anyone know what could be causing this? I just bought this truck and have a few months of powertrain warranty on it.

well if it is under warranty I would just let them look into it. Might save you some trouble.

Sounds like a issue with the converter as it locks up.

I had the same problem on my 88. If it is a 700R4 tranny it could be the valve body not moving enough fluid to shift into overdrive. Take it to a tranny shop and have them look at it.