Pulling a 5th wheel on level highway
I have a 30' 5th wheel and pull it with my Dodge diesel truck. The rear end gearing is 4:10 and the trans is an automatic which has been rebuilt for heavy towing. I was told recently by an experienc...
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psuce wrote:
This^^. Without knowing your tire size, but assuming a near "stock" size, your RPMs got to be around 2,400 in 3rd and 1,700 in OD. The 1,700 is much better scenario for the Cummins and will also net you better fuel mileage. Also 1700 is closer to peak torque.
I had a 2002 Ram 3500 dually with the Cummins HO and NV5600 6-speed manual with 4.10 rear axle. 5th gear in the NV5600 was 1:1 (direct) with 6th gear being an 0.73:1 overdrive. The 47RE 4th gear (OD) ratio is 0.69:1, very close to the NV5600 6th gear.
In 6th gear with LT235/85R-16E tires, my 2002 turned 2000 RPM @ 60 MPH, ~2170 RPM @ 65 MPH and ~2330 RPM at 70 MPH. The OP's truck should run slightly less in 4th (OD).
Rusty
