auto trans vibration

My Dodge Wagon Ram Van, 1999, was built for export only in the US. I purchased it here in Mexico where I live. It has been a good vehicle until this year. My current problem is a vibration in the three-speed auto transmission. It usually happens when I slow down for a speed bump, then acclerate slowly. At this time it usually is changing from first to second gear. At that time the transmission vibrates. If I accelerate, the vibration stops. A transmission mechanic here changed out the kit, but it didn't correct it. I then mentioned specifically the problem, had him ride with me while it did it, and he claimed he had fixed it. He said it was a stuck or sticking valve in the transmission. That was a month and a half ago. Guess what? It's doing it again. Suggestions?

Tenecmisionero

Check the U joints. And find a new mechanic.

is it a vibratiion or shudder .... vibration you would feel throught the steering wheel or throught the seat, shudder would be the van jerking back and forth