Torque Converter

 

Torque converter. I wasn't aware they could be a source of vibration - never owned an auto trans car or truck (really). I love the degree of control a stick gives.

I replaced my Blazer's diff cover with a finned aluminum one with a drain plug; don't remember what on line store I found it in, but they are available. It also holds about 1 qt more oil - no more clutches locking up at random in there.

Your vibration could be a # of things - bad u-joint (s), axle runout, thrown driveshaft weight, bent rim etc.
A detailed description might help someone here help you

 

Maybe a fly wheel crack? You can remove the inspection plate (pop it off) & have someone bump the engine over in steps & look inside with a flashlight at the fly wheel.
Just unplug the coil so it doesn't start.

 

IT can also be damaged hardware on the converter.

Best to pull the fuel pump relay so she dont flood on ya . Pulling the coil wire is not a bad idea either.