Stabilizers are not leveling jacks. The only jack on most travel trailers that can actually lift – is the one on the front A-frame. I’ve seen ads for travel trailers with auto-leveling jacks – but have yet to see one in person. Suffice it to say, almost every travel trailer has 2 or 4 stabilizers and one jack. You level side to side by pulling one side or the other up on leveling blocks, disconnect, then adjust front to back height with the front jack. THEN put down the stabilizers.
Fifth wheels have some combination of stabilizers and jacks. Some just have jacks on all four corners or even six jacks for the big ones. These can actually level, but as described in the stories below – you probably shouldn’t be lifting tires off the ground. Thus, I’d say, the same thing goes as for travel trailers – if the side is very unlevel – use boards under the tires to get close to level before engaging the level system.
When we had a large Class C, we boondocked at the Buffalo Grasslands site north of the west 
Badlands gate (south of Wall, SD). Those of you who have been there, probably remember the point on the south end. It was a fantastic view if you could park there. The problem was, on a fairly long Class C – the rear wheels were 6 inches lower than the rear (backed in) as well as the east side being lower than the west. That didn’t stop me from piling every board and spacer I had under the wheels, backing on to them, then more blocks under the jacks and jacking it up and putting more boards under the tires. In the end, we were fairly level. Two problems: first – RV chassis are built with the wheels on the ground and the weight distributed across the chassis supported at multiple points via leaf springs. The rear jacks attach at a single point, each side, to the frame behind the rear axle. Then end result of too much weight on the jack, is that your frame flexes in ways it wasn’t designed for and it forces everything above in the RV to flex with it. I wonder sometimes if this is the cause of exterior sidewall cracks that people see on bigger class As. On our C – the frame flexed so much the bathroom door wouldn’t latch. More on this below.
The second problem, particularly in a place like the Badlands – is wind and rain. Stacking your RV on top of block after block after block – jacks or not, makes it less stable, on a cliff…. We got hit by a gust front from a major storm while we were there – one we were worried enough about that we pulled in the slide. Fortunately, everything held, but if the blocks had slipped or given way – it wouldn’t have been pretty. Our next trip to that site, we stayed on mostly level ground, well away from the edge.
So, that was a long time ago – many campgrounds and many boondocking locations past. But you’d think I’d remember….. We were at a spot last week where the only place (every place) was pretty slanted. We ended up at a spot where the right side, particularly the right rear was quite low. Despite driving up on two layers of blocks, after auto-leveling, we ended up with the right rear tires off the ground. So, while they were up, I put another board under and we let down the jack on that side some so the tire was in contact. We weren’t perfectly level but we were “close enough”. The problem was, that we left too much weight on the jack and not enough on the tires. We didn’t notice right away, but eventually, Debbie noticed the bathroom wall was pulling away from the sink/cabinet. Almost half an inch. That was just before we left. By the time we were set up at the next camp, it has returned to its normal position – but it was another example of how too much weight on a jack and not enough on the tires can warp and maybe even break side-walls (and who knows what else). It makes me think about taking a good look at the roofline for any broken caulking. The RV “house” is built on top of the frame. Change the shape of that frame, and it is going to stress the other sides of the box. The short of it is, even jacks which CAN lift a corner of the vehicle off the ground, should only be used to extend the wheel down a couple of inches.
I’ve seen some weird leveling and stabilizer boards. Jengo-like stacks of 2X4s, 12x12x12 wood blocks, log rounds, cinder blocks, the usual yellow and red lego blocks and these “I” blocks.->
Whatever works I guess…..
Along with a few boards I had in the garage, I went to the HW store and picked up a 12 ft 2×10 and 2×8 and had them cut into pieces right there. Smaller 8×8 pieces are good for the jacks and two-foot-long 2x10s can be used either direction under the dualies. But no matter what grade of lumber I buy, these boards tend to split down the middle over time. As a “cure” for this splititis, I picked up some 3/8ths threaded rod and a long 3/8ths wood drill, some washers and nuts. The hard part here is drilling straight through the board. Mostly I eyeball the alignment carefully from every direction as I drill through. Sometimes it helps to simply drill in from both directions after drawing a line and double-checking.
Then push (add a couple of nuts and a hammer) the rod through and add a washer and nut to each end. Tighten as much as you can with a standard wrench or socket wrench and cut the rod off flush. This process works best before the board has broken, but can be used afterward too. Some glue might help if working on split boards. I’m still using the first board I did this to, a year later.
Yes, these boards are fairly heavy – so don’t go overboard. At a minimum, I’d want enough to raise one side, two boards plus a board or two under one side jacks. Worst case, three wheels, two boards is enough for the vast majority of sites. And save whomever is driving the RV up on boards some hassle – and set the boards so the tires can go up on one, then the other. It is hard trying to climb 4 inches of boards on multiple wheels and the STOP, literally on a dime on top. Your RV doesn’t HAVE to be perfectly level. I also carry a set of those red (heavy duty) lego block style levelers. I don’ t put them under the tires, but on top of a board, they work fine for the jacks. Because they are hollow on the bottom – they don’t work good on soft ground unless they have boards of some sort under them. Finally, I’ve never done it myself, but an alternative method for an unlevel boondocking spot is to dig a shallow depression where the highest wheel will sit. Just fill it in when you leave. 
Last, in the What The Heck category – here is something I saw a couple of camps ago. This was a large diesel class A. Count them; there are three extensions, with a tow bar at the end. There is a receiver lift(with rock guard), a doubler (with a bike rack on it), another extension, and the tow bar has a long reach shaft as well. It has to be 5 feet of extension just to the tow bar, and I bet the entire setup weighs 500 pounds. He has clamps at every connection to try to reduce the slop that is always in receiver connections. And to top it off, he was towing a full size pick up truck. Please don’t be this guy.
mike
