94 4.0 5spd. Shakes when accelerating above 30mph.

[Bd30]

So when I drive no matter how smooth the road and get above 25 or 30 mph the truck starts to shake. The whole truck. It can be felt in the front seat and back, the steering wheel and floor. This only happens when picking up speed. Let off the gas and it goes away. Take it out of gear and it goes away.

The trans came from an other truck and worked perfectly. Clutch is brand new, u joints in both shafts seem fine, tires are balanced, plugs are all good. I'm kinda lost. Mostly because I know it has to be an engine problem. The fact that taking it out of gear makes the shake go away means it's not in the suspension. It's only when I hit the gas. It shakes like I'm in the wrong gear. (Those of you who drive sticks would know this shake, if you did 30 and put it in 4th) it's that same shake. But I'm not in the wrong gear.

Even tho I knew it wasn't suspension. I went over everything and it all looks good. So could it be a coil pack? What's the best way to check that, could it be as stupid as wrong gap on plugs?.... im lost

 

[TxGasRacer]

http://easyautodiagnostics.com/ford/4.0L/index-of-articles-1

 

[Tedybear]

If you think it's a miss fire, one of the ways I used to figure out what was going on was with a mist type water sprayer. Give the electrical area (coil, plug wires, etc...) a good misting with water. Doing this while it's rather dark outside might have things show up better. If you have any high voltage secondary ignition grounding out, that should make it show up.

It could also be "Lugging". Might want to check the fuel system and ensure it's not restricted (last time the fuel filter was changed? Pressure test on the fuel rail...etc...) It might be it's not getting enough fuel under heavy load.

Just a couple of ideas...

S-

 

[HER2702]

You say the trans has been replaced, make sure that your u-joints are 'phased' correctly. You most likely had to remove the 2 piece driveshaft completely from the truck. If any of the u-joints are not lined up correctly it can cause a shake