Are the shift tables in rpm? Mine are in MPH. The faster the engine accelerates the quicker the shift has to happen. Smaller tires will definitely affect this, so will gear ratio changes in the differential. I had problems bouncing of the rev limiter when I changed to 4.88 gears. I tuned it out in the summer but found that when it got colder I would hit the rev limiter again and had to lower the MPH that the shift would happen.