So I had the fluid changed today, and we found out what the vibrating is coming from. One of the previous owners did a shade tree lowering to the suspension, and removed a leaf on the rear springs, which has made them very weak. When going from a dead stop, due to the weak springs, the truck is squatting more than it should, and it's pushing the drive shaft into one of my exhaust hangars. I've decided to replace the whole suspension front to rear including upper control arms (Moog), lower ball joints, and rear leafs. I'll also be adding traction bars to keep the axel from rotating. All parts plus the 2/4.5 lowering kit have been ordered. I also had the front wheel bearing hubs replaced today, wow, I'm glad I did. The right you could barely spin by hand, the left, not at all. Previous owners have treated this truck hard, but once I've replaced everything, it's going to be like new.