Update
We finally put some real miles on the AWD GMC and could not be happier with the Van.
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A trip to northern Maine fall camping gave us a chance to realize how well a Van works compared to the Tent camping we also enjoy. We had 2 long days of driving planned and pulled the Van into camp at 9:15 PM by 9:25PM we were in bed, we woke to rain in the AM and were on the road in 15 min. We did have some apprehension about buying a fullsize Van, but the thought of packing up a tent in the rain and the time saved made it rapidly fade away that early wet morning.
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The mileage at 70-75 mph is 16.5 mpg dropping to 14.8 mpg in the mountains. (12.8mpg if you use the remote start while in bed to run the rear heater alot....
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...) The 5.3 and 3:73 gear did better than I expected in the mountains, it pulls the heavy Van 70mph up most grades at 2100 rpm in OD with the cruise on.
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The AWD and BFG A/T's did allow us to go down some big hills to remote river campsites and not slide on the mud and leaves into the trees . The GMC AWD 1500 may be just enough for our back country needs, we will see............