I just completed a 9,000 mile torture test of the G56 combo in the truck over 3 weeks. I took off from Michigan with my loaded 42 foot trailer, went down to South Carolina, down to Florida, over to California, up to Montana, and back home. All in all this truck saw lots of miles in the Rocky Mountains and Smoky Mountains, it saw both the Atlantic and Pacific, Both the Canadian and Mexican Borders, and crossed the Mohave Desert and several others. It climbed a private road with a loaded trailer 3 miles up a mountain with a 18 degree grade! It saw 113 degrees in Houston, and lots of traffic, hills, etc. I even hit an overnight severe sand storm north of Reno that covered the truck in a few inches of sand, and it almost tipped the whole thing over!
I am very very pleased with the truck and the combo. The extra gear made all the difference in the world. I can't even see ever towing with a five speed again. Downshifting is so much easier, and the Southbend Clutch is great. I have no complaints whatsoever. I'll continue to keep you all updated through the life of this truck and trans, but so far am a huge fan of the G56.