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...
Forum Discussion
RustyJC wrote:
The Dodge 47RH and 47RE (Hydraulic and Electronic) 4-speed automatic transmissions were modifications of the 727 Torqueflite (as used behind the 426 Hemi back in the 60s and early 70s) 3-speed automatic with an add-on overdrive 4th gear. This overdrive add-on was one of the weak links in this transmission, but with the 4.10 axle ratio in the OP's truck, the stresses on the overdrive unit when towing on a flat and level road are significantly reduced. Aside from that, towing at 65 MPH in 3rd with the 4.10s would have the engine speeds running significantly higher than necessary. Given the OP's setup, I would go ahead and tow in 4th (OD) under the speeds and level conditions mentioned until hilly terrain resulted in frequent 4-3 downshifts - then I might manually lock the overdrive out.
Rusty
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.
