Hi again. Went on a cruise yesterday with local group & the pointer. was doing some severe bouncing. Just purchased the 1951 3100 truck this week & the bounce came with the truck.

Vehicles of that vintage have a linear fuel gauge. If the fuel sloshes the needle moves in real time unlike modern vehicles. The manufacturers put baffling in the fuel tanks to minimize the bounce as much as possible. It's possible the baffling has come loose or it has an aftermarket tank that doesn't have baffling in it.

Thanks. Just purchased this truck this week so I will remove the 3 screws at top of seat back so I can see tank to check if it is new or not.
ol-nobull

Also keep in mind that the needle will move a lot normally when compared to a modern vehicle. It moves in real time so unless it's bouncing from empty to full all the time it just may be normal. It can be disconcerting to someone not familiar with it.