Verified answer

There are a few possible reasons. Your truck could be idling too high, you could have transmission fluid which is too thin (dexron will do it), or the splines on the output shaft from the transmission could require lubricating with moly-grease, also inspect the u-joints

You may have a bad ujoint if it is out and there is any slack in the joint it will pop loud and shake.

climb under the truck with the wheels blocked and the parking brake on , the engine dead and it in neutral.

shake the ujoint up and down and side to side if there is any slack or any rust coming from the cups the ujoint is bad

also look for a vacuum leak that may be making the engine to idle to high if you have a tach it sould be under 1000 rpms

check you trans or engine mounts, could be that the rubber has deteriorated and that could be the cause of your jolt or shake.

Idle is too high.