I own an 88 b2200 2wd long bed, have had it about 9 years, over 300,000mi & have done much maintenance/repairs from replacing rocker arm shaft assembly & cam(oil holes plugged & ran down cam lobes) to replacing the ENTIRE wire harness from engine compartment to cab & bed, & replacing the center U joint (only serviceable one) of the split driveshaft so I am very familiar with the truck. My question is just recently was driving normal commute, no abnormal load ect. & with no distinct or noticeable sounds jarring, or otherwise any indication , starts a very intense vibration that develops rapidly at about 10mph & above, though I haven't taken it much over 10mph, luckily I wasn't far from home when it started. It's more of a whole body/frame vibration. I'm familiar with the vibration of tire imbalance & this is much to fast at too low traveling speed for that, pulled driveshaft checked all U joints, carrier bearing, & balancing weights for any abnormalitys with no luck, the vibration is a very quick/short but high frequency suggesting that the imbalance is that of something with a higher (non-engine)rpm, doesn't seem to be transmission/driveshaft, I have an idea what the general cause is but I'd like to get professional opinion before I take on this project, as well of any insight of a more specific diagnoses if you could be so kind. Also in your opinion if this is a serviceable matter(for someone very mechanically inclined) or overall better as a replacement/salvage or junk yard swap-out project. Hope I've given enough detail, Thanks, Terry Spokane, wa