transamz9 wrote:
I don't think it would be an overkill really. I wouldn't want a shift able on the fly unit. Just one I could choose before I took off. I have 3.42's and although it does great at towing my rig I do lock it down in gears for certain things. when on the interstate I lock it in fifth and forth on the 55 mph roads and under. If I had a 2 speed rear I would just choose the lower side when I tow heavy and let the truck do it's thing. See my problem is that when in TH mode it won't shift to fifth until 55 MPH and 6th until 65 MPH so when I hit 56 or 66 it will lose speed on the slightest incline causing it to shift directly back down because it's under it's power band.
Cummins Powerspec recommends the 6.7L to be between 1,800 to 2,200 rpm when towing heavy. Not only does it make the truck more efficient when towing, but it also keeps the EGTs down. In a 4X4 Ram with the stock 33.2 inch tires and the 68RFE gearing, 5th gear would put you right over 1,800 rpm at 65 mph which is where you would want to be. A lot of people are hesitant to run the the Cummins in 5th only and cut out 6th when towing because they think running the higher rpms will hurt it or wastes full, but in reality it is the opposite. The 5th gear on both the Aisin and 68RFE are still an overdrive gear, and I told my customers to think of 6th gear as the overdrive when not loaded and 5th as overdrive when towing.
