[unclebubbles]

Before trying to diagnose a transmission shifting problem, always make sure the engine is running properly. Even though most late model computer controlled transmissions dont have a vacuum modulator, vacuum still plays a part in the proper shifting. If an engine isnt running right, the vacuum will be off for a given throttle opening, and this can cause delayed, harsh upshifts. A bad VSS can also cause harsh, erratic shifting, but make sure its running good first.