Chevrolet Astro Forum : “Wierd vibration”

Wierd vibration

1991 astro, 225k miles.

I've recently developed a strange vibration that occurs during acceleration; starts about 10mph and ends around 25 or 30mph. Feels like driving on those highway rumblestrips, and is worse the harder you accelerate. Is this the tranny? differential? ujoints? driveshaft? I can't afford a mechanic so I need to solve and repair this myself.

TIA for any/all answers!