The higher fuel pressure will not cause a shifting problem directly but it will cause a change in the "personality" of the engine. You will be holding the gas pedal in different settings. When the pedal is down further, as in harder acceleration, the transmission will up-shift later and with more force. The clutch packs apply harder and faster to reduce the slippage that takes place until they are fully applied. Under light throttle up-shifts, the clutch pack engagement is softened to give a smoother, more comfortable shift. I don't know how you found the fuel pressure staying too high so quickly but I suspect that is the cause of the change in shifting characteristics. Solve the fuel problem and I'll bet the shifting goes back to normal.
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Monday, March 7th, 2011 AT 10:31 PM