[Richard]

I hope this helps someone in the future. 

If you want to replace the salon slide out cylinders for an HWH slide, first be aware there are two mountings. The first, and like mine, has access panels in the basement ceiling and front tire well on the passeger side. Inside you will find the end of the cylinder mounted to the frame via stud on the end of the cylinder, and two large nuts for adjustment. If you have a later model HWH slide out, the nuts on the driver side, and I have no idea about that one. 

Here is the essence. HWH uses a different approach to hydraulics than most of us old tractor mechanics are used to. Both the extend and retract ends are pressurized during the extend stroke. It WILL NOT extend unless both ends are pressurized because there is a check valve apparatus at the rod end of the cylinder. It will retract by simply pressurizing the rod end of the cylinder. If you don't know this about HWH cylinders it causes a whole bunch of vocabulary expanding perjoratives. 

That point is essential in understanding the post. The instructions for installing the cylinder from HWH say to install it extended. Plus you have to extend the room to access the attachment point for the cylinder rod. However, with the rod extended you would have to cut the coach into two pieces to get the cylinder out and put a new one in. 

There may be other ways but here is how I did it. 

I used a port a power hydraulic pump courtesy of HF. To extend the cylinder, cobble enough fittings to get from the 1/4 NPT of the port a power hose to the 1/8 flare fitting of the cylinder. Cobble together enough fittings and hose to tee the hydraulics and apply hyd pressure to both fittings. It seems counterintuitive, but when you apply hyd pressure the cylinder will extend. 

To get the cylinder to retract, rework the hoses to only apply pressure to the rod end. Obviously hyd fluid will come out of the other end when you move the cylinder. 

As you extend the cylinder, you may have to refill the reservoir on the pump several times. When I had all the fitting arrangements to suit me, I extended and retracted the cylinder a few times will holding it vertical in both directions to bleed any entrained air. I was careful when installing to minimize the leakage while reattaching to the HWH system. 

You wil first need to retract the old cylinder to get it out of the coach. Then you will need to extend the new cylinder after you put it in place. Only after extension can you line up the attachment points of the cylinder with the coach and slide. 

My fear was that with a cylinder at each end of the room, that it would cock the room until the hydraulic system cycled a few times and bled out any entrained air in the replaced cylinder. With the careful bleeding on the bench prior to install, the room did not cock when moving on the first trys. 

There may be a simpler way, now that I have slept on it. It may have been possible to open the access above the tire, disconnect those lines and cap them. I may have been able to simply press the extend and retract buttons to operate the cylinder I was working on. I do know that I tried to use the HWH pump and system to move the cylinder when it was mechanically disconnected on both ends and it started to move the opposite end of the room. I decided not to pursure that approach very far. 

The post begs the question, why did you change the cylinder? It was not appreciably leaking. However, the room was cocking a bit going in and out. Cocking enough that the outer skin of the slide was catching on the coach skin. I knew that was going to create a big problem eventually. There is an adjustment in the center of the slide, up in the ceiling to account for cocking, or racking. However, that did not address my problem. My specific problem was the rear would start out late going out, but also start out late coming in. Meaning the room was racking in both directions. The only thing I could figure that would account for that was that the seal inside the cylinder was leaking by causing the cylinder to react slower than it's counterpart. 

All seems to be good on the test trys.