The Big Three's New Diesels put on a Dyno

ShinerBock wrote:
To continue what I said above, here is the mph that each truck can stay in gear. I don't know the max engine speed of the GM so I am just going to assume it is 3,000 like the Ram. If it is higher then it tilts this in favor of GM being first up the Ike even more.

Ram Aisin
1st 3.75: 0 mph-19mph @ 3,000
2nd 2.00: 19 mph @ 1,650 - 35 mph @ 3,000
3rd 1.34: 35 mph @ 1,950 - 53 mph @ 3,000


GM Allison
1st 3.10: 0 mph - 25 mph @ 3,000
2nd 1.81: 25 mph @ 1,800 - 43 mph @ 3,000
3rd 1.41: 43 mph @ 2,300 - 56 mph @ 3,000

So as you can see, due to the taller rear gear and the Allison's better gearing spread(which is almost identical to Ram's 68RFE). The GM truck was not only able to stay in a lower gear (with more torque multiplication) at higher speeds, but it also started the next gear at a much higher rpm pitting it closer to peak horsepower.

In contrast, the steep 2nd to 3rd spreed on the Aisin along with the shorter gear ratio forced it to shift up to 3rd at a lower mph and put it at a much lower rpm making less horsepower.

The GM Truck ran the hill in third gear, same as the other two. My DMax/Allison won't downshift until right at 2000 rpms.

Rich