getting vibrations..........
...IT'S NOT..
wheel balance (done 3 times)
alignment (just done)
Carrier bearing (just done)
u-joints (no play, inspected at time of carrier bearing install)
no vibrations in neutral at speed (not in tires, wheels, bushings, radius arms etc)
no dents or weights missing from drive shaft

was only vibrating at light load 35-40..would not vibrate if i gave it more gas to power through that range.
now it is getting more speed range.. (30 to 45)

wasted over $1,000 chasing it and recommendations from idiot service advisers..

1992 f-150 flareside extended cab 2x4 302 4 speed automatic OD (jasper trans)

 

Rotors and pads done recently?

 

I'd say rotors

 

Welcome to the club. I’ve had a driveline vibration that the dealer has had 3 cracks at. First rebuilt rear diff, all new bearings, pinion and ring gear. Nope still there - oh must be the front diff - so they do the same to the front diff. Nope still there. Says they checked the drive shafts when they had them off to do the diffs. Short story is they did nothing to fix it. It has changed a little, used to show right about 50 mph. Now it shows at about 63 mph and goes away when you let off the throttle. I am thinking either drive shaft needs to be balanced/replaced or the U Joints are binding. I have had the tires balanced several times at different shops and still there.
Like you, I don’t want to drop lots of money until I KNOW what the issue is. Mechanics can give you lots of guesses - I mean its your money not theirs, right?
Side note I know of one person that has the same truck and same issue as mine and they replaced the rear drive shaft and that fixed it. My truck is off warranty so too bad for me.

 

Having work "done" or parts replaced doesn't prove that it was done RIGHT, or that the parts are GOOD. If you can't inspect it, find someone who can, and pay him. Otherwise, get rid of the truck.

If you want help, you're going to have to spend a lot more time telling us what IS happening than what you think it's NOT.Alignment doesn't cause vibration, no matter how far out it is. Period. If it's bad enough for long enough, the TIRES can develop abnormal wear that CAN result in vibration, but then it would be the TIRES causing the vibration - not the alignment.

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That's still pretty vague. Click this, read all the diagram, and the whole caption (a few times if necessary):

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All that and a LOT more needs to be in your signature as this caption explains:

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Something that can ALLOW normal vibrations to become excessive (and which commonly DOES on these trucks) is the engine mounts, and it fits with the symptoms you've described so far. But DON'T rush out to have them replaced - INSPECT them first (it's easy):

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This aftermarket design absolutely eliminates that problem, virtually forever:

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