If U were spec'ng a truck for fuel mileage...

Ever try and back up in high range reverse? Boy will that get away from you fast!

 

Did ya ever shift 3 times going backwards ? Dang i sure liked them 6X4 two stick setup

 

Yep in a Mack 12 spd. That truck would get done going backwards 5 shiftable gears in reverse + 1 deep reduction gear.

 

Saw the video on PP's website about the 389 glider kits with the pre emission Cat combo. Honestly, I would spec a forward lift axle for the tractor. My choice of truck would be a Pete 386 or Freightliner Columbia glider kit with a 13spd, 3:42 rear ratio, and a 12.7 Detroit 500HP, N14 Cummins Redtop, or 03 ISX.

KH

 

You took the words right out of my mouth... COOL

 

Browsing thru some old posts and noticed this. Its the same tranny Pittsburgh Power sets up in their Pete custom glider kit:

http://www.pittsburghpower.com/support/viewtopic.php?f=7&t=230&sid=cdb4c954b801063a52bec0a8ff956c81

 

I was thinking about that and how nice it would to be able to cruise at 70 mph and sit at 1300 rpm. Now what about when it came to climbing a good grade? I'm curious as to how far down you would have to drop gears. Now if I was an o/o I would not have a stock tune mine would be cranked way up but what if it was say a 475 c-15?

 

Hmmm....I dunno about all that. My 9400i is spec'd that way with the exception that I have 3.58s and 10spd/OD. 75mph was at 1700rpm and fuel economy would be more like 4.7-5.0, if I was lucky!

Cummins told me, about my 04 ISX 450ST, that 1425rpm is the "sweet spot". On my truck, that's 62mph.

 

Then I would spec the truck with some higher gears and make sure its an aero truck and set it up so that 1425RPM is right in the 65-68 MPH range.

 

Would you then keep the 10spd? I already checked the gear ratios available for my axles (RT40-145P) and the next step is 3.42s.