Overheating while in motion but not idling on 1993 Dodge Caravan

The engine starts to overheat whenever I am driving over 55 mph . Under that speed or at a light or in idle in the drive , there is no overheating . There must be some connection between the cooling and transmission but I don't know what it is.

Asked by for the 1993 Dodge Caravan
no, it is a circulation problem, you probably hae a clogged radiator. now that you have driven it overheated, you may have compounded the problem by doing internal damage from the constant overheating.
I had the radiator replaced but now the mechanic is saying that he needs to do the water pump . But if the water pump wasn't working ... then wouldn't it overheat while idling . And I never actually ran it over the H temp mark . I would turn the heater on and pull over until I could get it home so it never completely overheated .
1 more answer
So.....I posted an answer here but I thought it was for a Toyota Camry, so I checked (EDIT) and put this reply. MAKE SURE THE COOLING FAN IS KICKING ON. YOU SHOULD HEAR IT WHIRRRRRR UP AT HIGH ENGINE TEMPERATURES. The little things can be overlooked so fast, it'll make someone's head spin. Also, have the Engine Coolant Temperature Sensor replaced. The connector on them can get brittle from normal heat and age, which causes a bad signal to the computer. I just might save you more money if I caught this in time. Jay