lenr wrote:
I sure like the 6 speed transmission that comes with the 6.7 better than the 4 speed that comes with my son's 7.3. The narrow spread of the gear ratios are great for towing.
This is a big deal for me. I do a trip many times each year climbing over 7200 ft Donner Summit from sea level. There are 13 grades that require the truck to downshift from 4th to 3rd on the 4R100 transmission. Cruising at about 63, 1700 rpm or so. Downshift to third and now you are at 2300 and 55. Some of the grades it could pull in 4th if you started at 75 to keep the revs up. You could pull them at 65 if you are willing to run the engine 3000 rpm in 4th but I am not. 4th is 0.71, 3rd is 1.1 - that's a BIG gap. Another time, coming north against a 40 mph north wind, truck would not do it in 4th, had to run in 3rd for half a day.
On the new 6R140, 6th is 0.67, 5th is 0.86, and 4th is 1.15. The gap is plugged by 5th. Add that to about twice as much power and it feels quite different. Haven't been up to Tahoe yet with the new truck but I am expecting to be pleased.
Another difference: the 4R100 1st ratio is 2.71. On the 6R140 it is 3.97. No wonder it gets off the line quicker! I have been on one backroad grade (into Shelter Cove on the California north coast) that we had to pull in 1st gear, and I wasn't sure it would make it.
Not just the ratios but the transmission control is all around better behaved.
