Originally Posted by Rockjock3

I am an operations manager for my company and we have 22 vans. we have a similar symptom from time to time. Vans will be fine till you get to a range usually around 45-55, 40-50, 50-60, or something similar. At that point they start shaking, but if you ease off the gas and then go back through the range it is fine. If you keep going through the range, without backing off, then it gets worse. Every time it is either the tires (balance or wear pattern), alignment or joints. Those are a great place to start.