Driveline vibration out of now where! Help!

mopower440 said

it seems to have kind of a slight vibration going all the time, but the pulsating bad vibration comes in about 40-45 MPH and way worse in 3rd gear than second..I can run it up to 45 in 2nd and its not near as bad as when it shifts into 3rd and at that same speed.

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This is your clue right here.
After the trans shifted, nothing changed from the trans back.
At 42mph in second gear, the engine was at about 2500 rpm.
After the shift into third, the rpm dropped to about 1750, and the vibration was waay worse..

So now, run it at 1750 in the other gears and see if the vibration is the same or similar. if it is, then look to the engine or TC....If it is not, then I would suspect the vibration originates inside the trans, and oldkimmer may have nailed it