Truck camper off truck on slope

What size camper?
Having big campers - I had to straight up the front jack more than once. It was dualy extensions that bend.
That said 2-ton weight is not something you want to fool with, so in your case I would build some high-friction pads that would make horizontal surface for your jacks.

not worth the chance of dropping it.

You have to check to see if it slides. I'd at least put something like rubber or stall mats under the jacks to prevent them from sliding. My driveway has about half that slope, but I've never tried taking it off. My street is almost flat, so I do that instead.

You could try jacking it up to see if it stays put or not.

I've unloaded/loaded our 9'10" Lance a couple of times on mild slopes. It does not take much of a slope to cause problems. I would not unload on an 8 percent grade.

The main issue is the stress on your jacks when you rotate the camper from parallel with your truck bed to horizontal.

Good Luck,
Brad

The camper is a arctic fox 990.

I warped my two right side jacks doing that. Once there's weight on the jack it doesn't usually slide, so as you raise the other jacks to level it, a lot of side pressure is put on them.

Distance between jacks front to back is, depending on the camper, about 8 ft. That would give you about 10 to 11 inches difference you would need to raise it. (I'm estimating, not calculating)

I've never heard what maximum "out of level" condition should be safe for the jacks.

I wouldn't do it unless it's an emergency.

A mild north to south slope can usually be mitigated with a couple of leggos under the front jacks...Two and one half feet over thirty seems a bit extreme, JMO

3 tons

Depending on your jacks, when extended, they can flex. When raising the individual jacks on a slope, as the weight shifts laterally they can start "walking" down the slope.

Don't ask how I know this.....

Find another spot.

30” rise over 30’ is 1:12 or 8.33% slope or about 4.5 deg slope.
Not a big deal imo. Other than loading and unloading. Might be tough if the truck is a tall 4x4 and the back end is cranked up with air or springs before loading.
If it looks like the jacks don’t want to sit flat when you level it out , may want to shim up pads under the jacks.
It’s not ideal for loading and unloading but the camper won’t care when you level it out. Don’t tweak the jacks. 1” shim under a 12” pad will level the jacks if your slope is accurate.