'93 3.9 Low Rumble from Engine

Engine is a high milage (over 150,000) one. Truck is manual transmission. Above 2000 RPMS, low rumble noise and vibrations felt through gear shift lever.
Only hear it when engine under load. Ideas? I think its worn crank bearings...

it could also be worn bearing in transmission or low fluid or maybe a bad u-joint that is only stressed under load. worn engine bearings usually result in a knock or thud sound not a vibration

Thank you for the reply! Was hopin it ain't the crank/cam bearings! Will check the U joints then figure out how to check the transmission bearings!