The Stovebolt Site Forums The Shop Area Driveline bucking at slow speed (1949 3100)

I have a question for the knowledgeable people on here. When I slow down the truck, "bucks". Does it worse in 3rd gear, but also in 2nd. Not as noticeable in 1st. What would cause this? Clutch, rear end? My 1938 doesn't do this. It just chugs along. Thanks, Grady.