Hard Shifts.

So I just bought my 2002 Grand Prix GT. I noticed that after the car warms up and a few miles have passed the transmission begins shifting harshly. Now from what I've read on here it seems to be the EPC solenoid, I am noticing a high pitched squeal, but not really a whine. This is the only problem I am seeing so far, so am I correct in suspecting the EPC solenoid?

Is this the solenoid I need :

EPC Solenoid

Also does anyone know if the Haynes manual covers replacing this solenoid? If not does anyone know of a how-to/walk through they can point me to?

Thanks,

Eric B.



Edit : Is there an updated part that shouldn't need replacing again?

If you click on the 4T65E Info link in my sig you will find info on your condition.

I read the information. I actually took the car to Aamco today and they kept it overnight and drove it and ran their scan tool on it. They found nothing wrong, no codes or anything. Would adding Lucas Transmission stuff help any? If so do I need to remove a qt. before I add the bottle? Is there anyway to disable the code that gets set in the PCM/TCM at all?