Truck shakes when in 3rd or final gear. When I shift it in second it won't shake at 45. If I press the gas and make the truck shift from 3rd to 4th it will stop shaking then start back up. Is it the torque converter or trans? Or u joints?

 

Place the truck in neutral (while traveling at 50 mph) and see if the vibration still exists (if it does- engine or drivetrain)...if so, gently rev the engine to see if it changes (if no change, its the drivetrain or wheels)

if no symptoms show, its likely plugs/wires time, lazy egr valve, perhaps a fuel injection service.

 

Great idea. I'll check first thing tomorrow.

 

That doesn't make sense.

When you put it in neutral at 50 MPH if the vibration still exists then it ISN'T the engine. If it still vibrates it is something downstream of the engine. If the vibration goes away when you shift to neutral the problem is in the engine.

 

Sorry about that...I said that backwards!

 

Ok so it only shakes overdrive.

 

It goes away when you shift to neutral?

 

Yes or downshift.

 

That means it's the engine causing the problem. Most likely a misfire.

 

^5

 

This forum always fixes every problem lol. Took the valve cover off and one of the injectors was unplugged. Thanks for being dead on with the advice!