1995 Ford F-150 45/50 mile shakes

What engine do you have? 5.0 or 5.8? Am I correct in assuming it is the engine that is shaking and not anything in the suspension?

A couple of questions: it shakes at 40-50mph with the OD on, and at a lower speed with the OD off, right? What lower speed does it shake at? Does it shake while accelerating, at cruise, decelerating? And very important, does it shake while in park, and if yes, at what rpm?

We'll try to determine if the truck shakes only while driving, at what rpm do you notice it, when it's the worst and if there's noises along with. Since we're not there to actually interact with it, you'll have to tell us anything that might give us a clearer picture of what's happening.

We're trying to determine if the shaking is strictly in the engine, somewhere else in the drivetrain or in the suspension somewhere. It sounds to me like the shaking is related closely to engine rpm, but only happens while driving at certain speeds. Am I right?

If it were in the engine, the engine would shake at a certain rpm regardless of whether the truck is in park or any other gear.

If it was in the suspension or out of balance tires, the truck would shake at certain speeds regardless of whether the truck was revving at 6,000rpm or coasting at idle. Or anywhere in between.

If it was in another part of the drivetrain other than the engine, the truck would most likely shake while driving AND at certain rpms. From what you describe this sounds most like your condition. The first thing that comes to my mind is either a bent/out of balance driveshaft, or if you have a two piece driveline a worn carrier bearing where the two halves come together.

Also, if your truck's stock suspension has been changed in any way, (lifted/lowered) then you could have U-joints that are operating at too steep an angle and so inducing a vibration. This type of vibration will get worse as speed increases especially if you're accelerating rather than just at certain speeds, so it doesn't sound like your problem, but it's just something to keep in mind.

Get back to us with what you think.