This article refers to full sized slide on campers that are big enough for two people to travel and live in comfortably for prolonged periods. Typically they would have a North/South queen sized bed, a shower and toilet, adequate water supply, a decent refrigerator and be electrically self sufficient.
As a general rule such campers would weigh upwards of 1200kg. For example our Northern Lite 8-11 Australian Ultimate weighs in at 1150kg dry weight (they weigh each camper as it leaves the factory). By the time it is fully fitted out and loaded ready to go, it weighs closer to 1600kg, and these are the lightest (and strongest) campers in this size range! So you need a vehicle that can carry that weight at least.
You can't rely on the vehicle manufacturers to tell you the legal payload of their vehicles. John Burke from Specialised Vehicles told me he had weighed most of the makes and models and not one can carry the advertised payload, not legally anyway, irrespective of what they tell you. The legal payload of a vehicle such as the Ford Ranger can be easily calculated. First you weigh the vehicle, with a passenger if you intend taking one, and then you deduct that weight from the Gross Vehicle Mass (GVM) stamped on the compliance plate. That is your vehicle's payload. John was weighing them without a driver or even a tray and they were all still well short of the quoted payload.
Now you have to consider whether you want a 4 wheel drive(4WD) or a two wheel drive (2WD). You can take a 4WD to a lot of out of the way places, even with the camper on and towing a boat. I have been to a lot of locations where you don't see Motorhomes, 5th Wheelers or Caravans and of course I needed a 4WD to get there. That said 4WDs are more expensive to buy and actually have a smaller payload than their 2WD counterparts. If you intend to stick mainly to the bitumen with a few trips up a gravel road, then a 2WD will serve you better.
There are more 2WD vehicles to choose from than 4WDs. There's the Ford Transit, Mercedes Sprinter, VW Transporter, Fiat Ducato and Iveco Daily to name just a few. Then there are the 2WD versions of the Chevrolet Silverado / GMC Sierra, Ford F Series and Dodge Ram if you want the luxury and power.
Most people seem to prefer a 4WD for their Slide On Camper. There are a lot of places you just can't go in a 2WD and many of these locations easily accessible in a 4WD even with the slide on camper loaded. I have been to many and you don't see a whole lot of motorhomes or caravans. I have even taken my slide on camper, with the boat in tow, to the top of Fraser island.
Of course the obvious choice for 4WDs would be the Ford F250/350, Chev Silverado and Dodge Ram, but in my opinion, they are overpriced. They have all the bells and whistles and the comfort and power is superb but US$50,000 turns into $160,000 by the time it gets to your driveway. Repairers and spare parts for these vehicles are scarce. I had problems getting my F250 repaired in many areas of Australia but then again I had the same problems with a Mazda BT50 and also the Nissan Navara.
The Australian utes, like the Ford Ranger, Mazda BT50, the Nissan Navara, Holden Colorado, Isuzu D-Max, Toyota Landcruiser can all carry these campers if you have a lazy axle fitted. This applies to both 2WD and 4WD vehicles, however I don't know of any 2WD vehicles with a lazy axle. These 4WD utes with a lazy axle have been a popular choice for many people and for good reason. The cost of a lazy axle is only around $15,000. The ride you get is better than the American vehicles with standard suspension. The vehicle is only slightly longer than normal so you have a vehicle that is easier to drive, with or without the camper. Parts and service are more accessible and the total cost is about half that of the American trucks.
The 4WD ability with the lazy axle will not suit those who want to do the 'extreme 4WD thing' in the mud and vertical rock climbing, but it has never stopped me from going to places I wanted to go. The lazy axles of today are much better than those of yesteryear with articulated springs, air springs and load sharing.
The people that fit lazy axles, like 6 Wheeler Conversions in Toowoomba Qld and Specialised Vehicles in Orangeville (Camden) NSW advise they can't fit lazy axles to Mitsubishi Tritons, Great Wall and surprisingly Hi-Lux. Apparently even with a lazy axle. these vehicles cannot carry the weight. Not yet sure about the new VW Amarok.
The Iveco Daily 4 x 4 is now a possibility. We looked at these when they first came out but they were too high, which would have made them top heavy and a bit tall for service stations and trees, not to mention problems with loading the campers which are designed to only lift a metre or so. Their was also a question of the actual payload. The new models seem to have addressed these issues and we will investigate these again. When it comes to 4WD ability, these will even satisfy the 'extreme' 4WD enthusiasts.
Other options include the Fuso Canter, Isuzu NPS and Iveco Daily 4WD which can all readily carry the load but they are big and not to everyone's liking.
One of the big advantages of a slide on camper is the fact that you have a vehicle to drive when you get back from you travels unlike a motorhome that just sits in the driveway. You may not find the bigger trucks as useful to get around town in.
In summary, the Ford Ranger, Mazda BT50 and Isuzu D-Max fitted with a lazy axle would be my choice, based on ability to carry the campers safely with a stable ride, service and support more readily available and the cost factor.
The American trucks are great with loads of power and great comfort and certainly the way to go if money is not a key consideration.