untraceable

9th and 10th even usable with a 3.15 rear end? cruising at 70 at 1300rpm

mass-hole

The advantage of the 10 speed is that you have a lot of intermediate gears so you can have a low 1st and a tall 10th and not have huge gaps in the middle. This is exactly what they did and it means you can run the same or lower axle ratio than you had and still have solid off the line performance while having a supercruise 10th on the highway.

Whether its needed or not is a different story. I guess if I was doing it I would go with the 3.15 since the highways around me are 75-80 mph speed limits and it would seriously drop my RPM's from my current 3.73/6 speed combo. I dont really think 1st gear is the issue on these trucks, its cruising along at highway speeds with a brick behind you. With the 10 speed, 8th is like a 5.5th, 7th is just shy of you old 5th, 6th is basically your old 4th, and 5th is a 3.5th. You basically now have half steps so it should be more than enough to get you the right total gear ratio to do whatever you want.

The only issue may be that you may end up cruising along in 8th when towing since 9th is taller than your old 6th. With the 3.55 your 9th would be your old 6th basically and you could still use 10th. I guess you should decide if towing or daily driving is your priority.

atwowheelguy

Towing is 10% of my annual mileage.