99 Mustang auto transmission problem

My auto transmission seems to be acting weird. As you are driving along it randomly down shifts very erratically. Feels like the car suddenly bucks a
few times then it goes back to normal. No lights or codes have been set. Car has 235,000 kilometres on it. I have had it to a transmission place, and just like going to the dentist, it would not do it while he had it. He checked the tranny for codes and nothing. Only thing I had done last year was replace the shift cable.
Any suggestions as to what the problem might be?
Don
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On Mon, 18 Aug 2008 09:35:38 -0500, "DonTraboulsee"

I'm guessing a bit here but I think these transmissions are controlled by an electric box on the side of the transmission. It's got some switches and gizmos in it that control the solenoids on the inside of the transmission. If the switches and stuff in there gets intermittent the transmission thinks you are moving the selector lever and shifts the transmission. If it was mine I would definitely quiz the transmission shop about it. I think it's less then $200 for a new "box" and it should be relatively easy to install, at least compared to rebuilding the transmission.
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