By I have a 98 dodge ram 1500 with a 318 v8 and I have a issue when I drive the truck and it gets about 70mph it starts to shake bad and that I put it into overdrive and it stops Idk what the problem would be bec I replaced spark plugs and spark plug wires and the distribator cap any help would be awesome

 

Without more details , I'd say check your plenum gasket and then the Cat

 

Idk about the cat bec that wouldn't explain taking it out if overdrive and it stop shakeing

 

Sounds like death wobble and likely has nothing to do with shifting into OD or not. Is this a 2WD or 4WD truck? How many miles are on it and has any front suspension work been done on the truck lately? How are the front tires on the truck - are they in good shape and properly inflated?

 

Sorta does . If the cat is restricted , and your doing 4000rpm , the exhaust may not escape but does have enough flow for lower RPM .

 

Its shaking right ?, not a miss ?. I would have the tires balanced, check the ball joints, and maybe even the hub bearings.

 

Hey I just hooked it up to the computer today and it says miss fire on cylinder 3

 

Then it is likely a plenum gasket issue. A symptom of a blown plenum is a slight misfire that is magnified in overdrive, causing the truck to shake in a similar fashion to death wobble. Just to be clear, you did mean to say that the truck shakes only when in overdrive correct? And it stops when taken out of overdrive?

If so, this is a sure-fire symptom of a blown plenum. Order the aluminum plate kit off of ebay and look in the DIY section of this forum for instructions on how to install it. Clean out your throttle body while you're at it and you'll be good to go. Let's hope that your cat hasn't already been ruined by the blown gasket...