OK here is what my truck is doing....First thing i started to notice was that it seem to shift into overdrive to early....then after about a week doing that then after it would shift into overdive to early then the truck will shake pretty noticeably until you hit about 50 then it goes away or if u mash down on the gas and make it downshift it would go away also...i figured i need a tune up so i got new wires, plugs, cap and rotor. but that still didn't fix the problem. so now its just been a guessing game and can't stand it no more. had a muffler guy look at it and he though maybe a torque conveter? but he was not sure! i was thinking maybe a fuel injector or fuel pump and the only reason i say this is becasue when i first start the truck up it fires up then it acts like it about to die then catches and is fine. and sometimes when your driving and have the gas at a constant speed say 35mph the truck hesitates. not a miss but more like a lack of fuel. well if you guys have any clue as to whats going on then please write a post. but most likley will be taking it to the Dodge Dealer for a FREE Inspection lol.

1999 Dodge Ram Sport 4x4 318

 

You check the motor mounts? When I owned my neon at a certain RPM it was vibrate like a mother. But after that it wouldnt shake anymore. Its a possibility.

 

Another possibility to check is the fuel filter if its hesitant at idle.

 

1st place i'd start is check your codes... try the key on-off-on-off-on method and see what it says...