Hi, I'm new here and have a 1993 Dodge Ram 150 pickup. It's got the 5.2 V8 Magnum engine and automatic with no overdrive (not that i'm aware of anyways). Anyway I'm having a problem with it. At about 60 to 70 mph if i try to hold it at a constant speed it starts to shudder like there's a miss in the engine. It seems like it goes away if I press harder on the gas. If I let go of the gas pedal it shakes violently until it gets down to about 50mph. I've replaced the cam positioning sensor, all 8 plugs, all wires, air filter, AND all my injectors (although the injectors were from a salvage yard). And it's still doing it. I'm about to lose my mind here. Any suggestions? The only thing I can think of is perhaps a bad head gasket. Please help !!! Thanks !!!

Spongehead

 

check the drive shaft

seen it before where the drive shaft has had a stuff support bearing. under power they are allright but under no load they shake like ****