I will admit that there was a time when I first got my truck that the 3.42 gear was too tall of a rear gear. After towing my 13k RV, 10k (loaded) cattle trailer, and various other trailers, I no longer think that the 3.42 is too tall. Especially when I compare it to other friends that have 2010-2011 650 lb-ft Cummins with 3.73's. My 800 lb-ft Cummins with its 3.42 gear sends more torque to the tires in every gear than the 2011 650 lb-ft Cummins with 3.73's.
Ram 2014 2500/3500 6.7L CTD 800 lb-ft @ 1,600 rpm with 68RFE with 3.42 rear ratio
1st gear--3.23: 2,584.00 lb-ft x 3.42 = 8,837.28 lb-ft
2nd gear--1.84: 1,472.00 lb-ft x 3.42 = 5,034.24 lb-ft
3rd gear--1.41: 1,128.00 lb-ft x 3.42 = 3,857.76 lb-ft
4th gear--1.00: 800.00 lb-ft x 3.42 = 2,736.00 lb-ft
5th gear--0.82: 656.00 lb-ft x 3.42 = 2,243.52 lb-ft
6th gear--0.62: 496.00 lb-ft x 3.42 = 1,696.32 lb-ft
Ram 2011 2500/3500 6.7L CTD 650 lb-ft @ 1,600 rpm with 68RFE with 3.73 rear ratio
1st gear--3.23: 2,099.50 lb-ft x 3.73 = 7,831.14 lb-ft
2nd gear--1.84: 1,196.00 lb-ft x 3.73 = 4,461.08 lb-ft
3rd gear--1.41: 916.50 lb-ft x 3.73 = 3,418.55 lb-ft
4th gear--1.00: 650.00 lb-ft x x 3.73 = 2,424.50 lb-ft
5th gear--0.82: 533.00 lb-ft x 3.73 = 1,988.09 lb-ft
6th gear--0.62: 403.00 lb-ft x 3.73 = 1,503.19 lb-ft
Not only that, but the 3.42 also puts you right in the beginning(1,850 rpm) of the 1,800 to 2,100 rpm in 5th that Cummins recommends for the best efficiency when towing at 65 mph. Even increasing my speed to 70 mph I am still within that range at 2,000 rpm. Not only is by buddy's 2010 5th gear sending less torque to wheels, but at 65 mph he is a little over 2,000 and at 70 mph he is past the efficient towing range at 2,200 rpm. So I got effiency and more torque.
I know a lot of people think the off the line performance of the Cummins has to do with the 3.42 rear gear, but if you tune it taking out or reducing the torque management then you will quickly notice that it is the torque management and throttle lag making it slower of the line, not the rear gear.