There is no "1500" 906 Sprinter. 2500 8550 GVWR is all the single rear wheel models, regardless of roof height or wheelbase (so even mine, which is the smallest 906, standard wheelbase, standard roof) EXCEPT for the "super singles", which are a 3500 single rear wheel but with a larger goofball rear tire that is nuts expensive and exclusive to JUST those, and of course since they are different than the front, no rotations. The 3500 dual rear wheels have all six same size tires, not sure of their GVWR but it is higher. They also get a 7500 pound tow rating ( regardless of engine or body) whereas the 2500 is only 5000 pounds (again, regardless of engine or body). Super Singles were only available in the higher roof and longer wheelbases I think. Which is odd, because the 3500 DRW was available in the standard wheelbase high roof.
I have never heard of any water pump problems, I will be on the lookout for that. All the 4 cyl ones I service have had exactly zero issues of any kind. And some of them are pretty loaded (HVAC company has theirs loaded down, ladder racks on top, etc., and they run them hard). I think our highest mileage ones are about 120k now. Sprinter forum has a couple running much higher than that, though. This was my primary reason why I wanted one instead of the V6, although the V6s have not been super problematic for us either aside from the early SCR stuff... although I did have to do a glow control module this week on a 2008... with 356k miles on the clock.
The new Sprinters' passenger version also lost the low roof setup, one more thing that makes mine one to hang on to. The Promaster is like that.
A coworker left here a month ago to move to SC to work for a van upfitter that set up shop 7 miles from the plant. They are doing all the new Amazon Sprinters.
They are not messing around, they've processed several THOUSAND already, with a bunch more to go... the plant is barely able to keep up.