Thoughts on 3.08 diff ratio

I figure that with an 18 speed, you have all those gears on the bottom that you never use....why not set up the rear diffs to get one on top that you never use in case of an 80mph light load/deadhead situation where you can drive fast and keep the rpm low.

 

Pancreatic cancer. It went quick. A coworker posted it last week.

 

In theory, changing the ratio won't really affect the speed you'll climb. If you're going to a taller rear ratio, you'll just have to drop to a lower gear in the transmission to throw the same amount of torque to the wheels. It should more or less balance out in the end.

 

Theoretically, they claim 16th gear (direct drive) has less of a parasitic power loss as the input and output shaft of the transmission are spinning at the same rpm. That’s why large fleets like walmart spec 2.64 with direct drive 10 speeds. This is why Cowpie built his truck with 2.64.....to eek out a little more efficiency.
ETA: also why they put your transmission in direct on the dyno.

 

Literally just put 3.08 and a 13 speed in my truck over the last month. I’m on my first trip now and absolutely love it!!!

It had 3.73 and a 10 speed before. 12 is almost exactly what 10th was before.

Added disk brakes too. there even better than the gears!!

 

Interesting, sounds like what I need behind my Cat if I decide to run a flatbed.

 

My 2020 T680 has 3.08 with a 12 speed automatic. 75 mph it doesn’t even get to 1400 rpm. At 65 mph its not even at 1100 rpm.
Pretty crazy but that is how they are now days.

 

At 1100 rpm you'd be getting some very good economy.

 

Yes miles per gallon are 8 to 8.5