Ok, so i have a 99 ram 15oo 2wd 5.2l that i picked up last night for cheap. only problem is when i am between about 35-55mph and with light to medium pedal pressure the whole truck begins to shudder violently. now if i give it gas or let off it will stop. also, it won't do it in 2nd gear at all. tires are brand new and even had them re-balanced yesterday. I caan feel a little vibration at all times but the speeds and low rpm i mentioned above it is BAD. I feel like it is the drive shaft but would like some opinions before i go out and replace it. and help would be appriciated.
I would like to add that it is not something I can really feel in the steering wheel, rather the entire truck from underneath. I know the kid I bought it from used off road alot as the tranny pan is modeartely beat up from hitting rocks and such.