Valley, neither cyl will have pressure until resistance is felt. If one cyl hits resistance it will stop or slow until the pressure is equalized in the other cyl. On that you are correct. That is simply how it works. In order for the cyls to move at the same time, they have to be connected by some mechanical means. Otherwise one cyl would fully extend before the other cyl would move. On a dump truck with a cyl on each side of the frame, the cyl are tied together by the dump bed and the truck frame. I am sure if you have paid attention to a loaded truck lifting the bed, one side might come up before the other side, same for the fel on a tractor. One side gets heavier than the other because of uneven loading, the light side of the dump bed or loader bucket will rise first, but the other heavier side will follow, so both cyl extend. This is because the cyl are mechanically tied together thru the loader lift arms or dump frame. Pressure will build evenly in both cyl because the hyd cyl are tied together with the hoses, but one cyl might extend first because of the amount of force required to move the load. The greater the distance between the two cyl, the greater the uneven lift will be, if the distance between the cyl is really great, the hoist could actually seesaw lift as the one side loads and unloads. A dump truck with a single telescopic cyl works similar. The shaft is hollow with other shafts stuck inside of the main, larger cyl. Because each shaft has a smaller piston size then the shaft it is inserted in, the amount of force is reduced for the smaller shafts. Therefore under load, the bigger shaft will rise first, same pressure, but bigger pistion, until the shaft is fully extended, at which time the next smaller shaft will extend and at its full extention, the next shaft will start to extend. Same principle applies to lowering the lift, the smaller cyl will retract first, even under a gravity retraction because the smaller shaft takes less force to push back into the cyl barrel.
