Yup just tested no change&the shake is kind of light...no noise never a back fire&even switched tires same thing...

 

That rules out the engine completely. With the torque converter remaining fluid coupled and just shy of stall speed any missing would be damped by it, so we're looking at things whose rotational velocity is directly proportion to road speed.

Silly things like a drive shaft being out of phase or slightly out of balance will do that, as can a slightly out of round brake disc or drum, having an odd lug nut somewhere (as when one is replaced with just whatever is available with the correct thread so it weighs more or less than the rest), a sloppy u-joint that's not making noise yet, a very slightly bent axle... the list goes on.

Sometimes it helps to isolate which end is weird by running in 4WD to the point where you expect the problem to occur. If the symptom changes, usually by becoming more perceptible in the steering wheel and sometimes by changing the road speed at which the symptom occurs, it's in the front. If it doesn't change, that doesn't rule out it being in the front, though. Do you feel it in the steering wheel at all? Usually getting into the vibration and then nudging the wheel left and right to take up slack in the steering components will make it more perceptible if it's in the front end.

If you go faster than the speed at which it occurs and then brake moderately to pass through that speed, do you get any pulsing sensation in the brake pedal? If so, it's usually a disc or drum at fault. If you don't get pulsation, it's probably not a disc or drum.

Chasing these things down is... oh heck, you already know how frustrating it is. Never mind.

 

it does seem to shake a bit when I apply the brake...also the shake felt @45 actually 47 only happens for a split second&from What I've heard on here is that it'll shake like heck if its a miss.

 

Sounds a lot like a drum or rotor. Some minor imbalances are undetectable except at the wheel speed that sets up a resonance.

You might pay attention to it with that in mind for a while to see if the supposition feels right, maybe try that nudging the steering thing while braking under conditions that will cause it to see if you get feedback there.

Usually it will, but it depends upon how consistent and how severe. Occasional weak ignition will produce a weaker symptom than a full blown no-spark condition. The telltale here that rules out a miss is that it happens at the same speed whether overdrive is engaged or not -- so at two different engine speeds, and whether or not the torque converter is in a state that would damp the vibration. That rules out everything upstream of the tail shaft of the OD unit.

 

okay so I did the test tonight and I pull a plug wire to see what it felt like while driving. right off the bat it was rough at idle, rough at all speeds 45 or so what's shaking but not like an earthquake but definitely not what I have been feeling.
also I forgot to mention lately around 70 miles per hour while on hwy truck seems kind of bouncing from the seat. when I did my front end work it wasn't much new tie rod adjuster sleeve and front end alignment new front shocks 2 and a half inch leveling kit body lift but I did not do the rear shocks& send this problem was there before the lift and tires maybe that could be it?
also like I said my Hvac control assembly is leaking and I need to replace it just can't find 1

 

If you've got bad shocks in just the rear you'll get a springy, sometimes bouncy ride. Just bounce on both sides of the rear bumper, and watch what happens when you stop. After the last downward force, the body should rise, overshoot just a pinch, then settle into its resting place. If it rises twice (up-down-up), the shocks are gone.

I wouldn't expect anything one might describe as a shake, though, from bad shocks. Bad shocks might make another problem more or less perceptible, but won't cause something like that.

I must've missed that tidbit. Vacuum leaks are ungood, as if it even needs saying. But unless it's really whistling at you I wouldn't expect it to result in the shakes except perhaps at idle. You could cap off the feed line under the hood though just to be certain.

 

Yeah What it is,is right behind the hvac selector **** there's that clear rubber piece with all of the vacuum lines for the diffrent selections its sucking from there You can hear it when You get on the gas its making a sucking sound...anyways so I couldn't get air through face vents so I switched it with another line to trick it I'm gonna replace the whole deal if I can ever find one.

 

Ok so today on highway around 60 the truck started shaking bad arounf
d 60 nomatter if od was off or on.I felt it through the floor&seat.

 

I don't mean to hijack this thread but I have also been having a prob. with my truck shaking around 45 mph. It feels like i'm riding on a wash board dirt road when it goes into O/D around 45, if i turn O/D off i feel just a slight "misfire", also when it is shaking, if i accelerate or let off the gas, it goes away. I have seen some post about doing a fuel sync but I don't know what year models that applies to. I did a tune up, and routed the wires according to the dodge bulletin and the owner before me thinks he might have moved the dist. but he can't remember. the old plugs were 1 year old and were not the normal tan/brown but more white/pink. my truck info- 95 1500 4x4 5.9 auto 33" tires 3.55G/R and a tons of miles