2018 Dodge 3500 dually gas motor row ratings

ib516 wrote:

RoyJ wrote:
Normally, I always correct people on the "torque vs HP" argument - as it's hp that pulls you up grades, not torque.

However, this is one exception where the TORQUE of the Cummins allows it for the much higher tow rating. An important spec in tow rating is startability - ability to pull away from a steep grade.

Cummins / Aisin: 930 lb-ft x 3.75 (1st gear ratio) x 4.10 = 14,299 lb-ft rear axle torque. With 33" tire gives 10,400 lbs of tractive effort.

6.4 HEMI / 66RE: 429 lb-ft x 3.23 x 4.10 = 5,681 lb-ft axle torque. With 33" tire gives 4,132 lbs of tractive effort.

The gas engine has only 40% of the starting tractive effort of the Cummins!

This means even with a 15,600 lbs trailer (23,400 GVW), the 6.4 gets beat off the line by a Cummins / Aisin towing 30,320 lbs trailer (39,100 GVW).

Simple math tells us the HEMI can only start out on a 17.7% grade, while the Cummins can pull away from a 26.6% grade!

In real life, the Cummins would perform even better as its torque peak (1700rpm) is much closer to the converter stall than the HEMI (4000rpm).

Unfortunately, your calculation completely leaves out the fact that all modern high torque diesels in pickups with auto transmissions are equipped with the transmission saving TORQUE MANAGEMENT (torque reduction) feature in the lower gears. There's no way you're getting anywhere near 930 lb-ft in gear 1 and 2.

I have actually tested it. In the real world. I used my previous 6.4L Hemi/4.10 vs a friends 3500 SRW Cummins/3.42. The trucks were identical with the exception of the transmission (66RFE vs 68RFE), rear axle ratio, rear suspension, and engine. We did 0-60 mph towing his 14k 5er. Guess who was faster to 60 mph? My Hemi was.

Unsurprisingly, I was faster 0-60 empty as well. That only makes sense. Lighter truck, 4.10 gears, and more hp.

There is a big difference between a 3.42 and a 4.10. If the Cummins had a 4.10 results could be different.