Mountain driving and towing with a gas class A

If it is a newer F-53, then by keeping the cruise control on will cause the transmission to downshift to maintain the set speed. This will apply going both up and down hill.

No issues pulling 3k# on the f53 provided you are within your weight limits. Going downhill utilize your tow/haul mode to leverage the engine brake. Pulling our civic down an 8% descent for 3 miles near our home on a regular basis I rarely need to even use the brakes. Aux braking system is usually a good idea though.

Here is my opinion. If the Class A Gas MH weighs more than 15,000 pounds I wouldn't do it. Not that you can't do it. But it is just because it would drive me crazy to drive a slug like that. Uphill would be frustrating. Downhill would very nervous. Downshifting will be your friend going downhill. Keep off the brakes as much as you can.

What is your rear gear ratio? Hope it is 4:56 or lower.

Towing a trailer? A Car?

Going up you'll slow down and downshift but it's not bad. Just need to be patient.

Either way you need brakes. There are some limitations on tongue weight to consider for towing a trailer also...