Artsyguy,
I will throw my 2 cents in. To answer a question in your OP, Is this normal? Unfortunately yes. I have a 2012 gmc savana 2500 and I also have a very steep driveway. Only about a 25 degree incline but still very steep, but it's only 75 feet long. I've backed on a fairly level portion of my grass and have been unable to make forward progress. Almost There hit the nail on the head. The rear end in these things are extremely light. The original tires are pretty sad too. Highway tires. I have planned my build to have several hundred pounds over the rear axle as Almost There suggested. Temporarily you'll need much more weight on that rear axle. We don't have lots of snow in winter but I park my van on the street if I think I have to go somewhere. Those street tires just don't cut it.
I will throw my 2 cents in. To answer a question in your OP, Is this normal? Unfortunately yes. I have a 2012 gmc savana 2500 and I also have a very steep driveway. Only about a 25 degree incline but still very steep, but it's only 75 feet long. I've backed on a fairly level portion of my grass and have been unable to make forward progress. Almost There hit the nail on the head. The rear end in these things are extremely light. The original tires are pretty sad too. Highway tires. I have planned my build to have several hundred pounds over the rear axle as Almost There suggested. Temporarily you'll need much more weight on that rear axle. We don't have lots of snow in winter but I park my van on the street if I think I have to go somewhere. Those street tires just don't cut it.