How To Level A Travel Trailer With A Slide Out

Everything on the standard leveling page still applies. What a slide out adds is a constraint on sequence and a reason to care about stability far more than a trailer without one.

Slide out: a section of the trailer’s side wall that extends outward on rails or rack-and-pinion gears to widen a room. It is a heavy assembly cantilevered off one side of the frame, which is why it is sensitive to the frame not sitting square.

Why the order matters

A slide runs on rails and is driven by a motor through gears, a rack, or a hydraulic ram. All of those designs assume the opening it travels through is square. When a trailer sits unlevel, the frame flexes slightly and the opening is no longer quite square to the slide box.

Three things follow. The motor works harder, because it is pushing the box through an opening that is now a few millimeters out of true — which you hear as a laboring or uneven noise. The seals compress unevenly, so the top seal may not contact across its full length and water finds the gap. And the box can bind partway, at which point you have a trailer you cannot pack up until you level it and try again.

The second effect is the one that costs money quietly. Slide seal failure shows up as a damp patch on a wall or ceiling months later, and by then the cause is invisible.

The procedure

1. 1

   Position and level side to side while still hitched

   Spirit level on the frame rail. Build the platform under the low side, supporting both wheels of a tandem axle at equal height, and drive up with the tow vehicle.
2. 2

   Chock all four wheels, downhill side first

   Chocks on the same raised surface as the tires. The tow vehicle is holding the trailer right now; the chocks are about to be.
3. 3

   Unhitch with a pad under the tongue jack foot

   Pad first, then take the weight. Release the weight distribution bars, unlatch the coupler and drive the truck clear.
4. 4

   Level front to back with the tongue jack

   Spirit level lengthwise on the frame. Get this right now; correcting it after the slide is out means retracting the slide first.
5. 5

   Set every stabilizer jack onto a pad, snug but not lifting

   Extend each jack until it is firmly loaded and the trailer stops moving when you rock it. Stabilizers prevent movement; they are not lifting jacks and must not be used to take out remaining slope.
6. 6

   Re-check the level before you touch the slide switch

   This is the check the whole page exists for. Both axes, on the frame. If anything has settled onto the blocks or into soft ground, fix it now.
7. 7

   Run the slide out, listening to it

   Operate it in one continuous motion and listen. A laboring, grinding or uneven sound means stop, retract, and re-check level. Do not push a binding slide through.
8. 8

   Support a long slide if the ground is soft

   On a long slide over soft ground, slide support jacks under the outboard edge reduce how much the frame carries cantilevered. Set them to support, not to lift the box — forcing a slide upward from below strains the mechanism as surely as an unlevel frame does.
9. 9

   Re-check after the first night

   Blocks settle, soft ground compacts and jack feet sink. Re-read the level in the morning and adjust, and always re-check before retracting the slide.

Packing up: the reverse order, and why

Retract the slide before you raise the stabilizer jacks or touch the tongue jack. The trailer must still be level and supported when the box travels back in, for exactly the reasons it had to be level going out. Owners who raise the jacks first and then discover the slide will not retract have created the one failure mode that strands a trailer at a campsite.

Then: jacks up, hitch up, bars on, chocks out, blocks collected. The departure checklist runs the whole sequence, and the slide line sits deliberately near the top of it.

The separate problem: rocking with the slide out

A slide out puts several hundred pounds a couple of feet beyond the side of the frame, which makes a trailer noticeably more willing to rock when someone walks across it. Two things reduce it, and they address different causes.

Stabilizer jacks on firm pads stop vertical movement at the four corners. X-chocks between the tandem wheels stop the trailer rocking on its own suspension, which is the motion most people actually notice and the one stabilizer jacks do least about. X-chocks and how they differ from wheel chocks cover that, and jack pads are what keep the jack feet out of the dirt.