I have a 1997 Dodge Ram 1500 with 4WD. I have a bad shimmy/vibration around 40mph/1500rpm, if you accelerate or slow down it will stop. When it starts vibrating if you push in the overdrive button it will stop but if you change speeds it starts again when you are in overdrive.

 

Inspect all front suspension first. If it moves, and it shouldn't, replace it. If it doesn't move, and it should... replace it. (have a friend help, makes it a lot easier.)

Make sure the engine is running good. (see plenum thread....) What you describe could be an engine miss..... getting any codes?

How are your tires?

 

Tires are new (less than 1,000 miles) no codes - new motor - was doing this before new motor installed - the front end is tight - I am pretty positive it is in the transmission, same problem before motor was replaced

 

Has the plenum been addressed? Did they transplant your intake onto the new motor? How's your cat? (the one on the truck.....)

 

Yes i am useing same plenum.Dont know about the cats will have to take it some were and get it check does the muffler shop do that? Can u send me the link on the plenum the threat i read didnt understand it.

 

Plenum thread is stickied right at the top of this forum. It's a common problem on the dodge trucks. (all of them WILL have it at some point.)

There was also a TSB (tecnical service bulletin) on plug wire routing, although, I don't think that is where your problem is coming from.

 

You can remove the extension housing on the trans and inspect it independently without having to pull the trans. But you'll need a press to remove the snap rings to get down to the o/d direct drum. Mine was doing that shimmy thing in O/D too and i presume it was related to my O/D direct drum snap ring snapping.

 

Was it overdrive problem?

 

Pull the rear driveshaft and check the pinon bearings, with the driveshaft out check all the cross-joints. check the trany mount as well. I see a new motor, does it have new, dizzy cap, plugs, rotor, wires? You might even wish to do a comp test on the motor. These trucks hide a miss very well.

 

New plugs,wires,cap,rotor,new motor was doing it before it put the motor in.