Towing in overdrive

Reply Subscribe

Thread Tools

Search this Thread

01-11-2005 | 04:47 PM

#31

kayjh

Registered User

Joined: Jan 2003

Posts: 202

Likes: 0

From: Canada

Quote:

Originally posted by Hannibal
Even my '05 Hemi 5spd auto tows our 10,040 lb high profile 5th wheel in O/D. It has a real tow/haul mode like DC should create for the Cummins. The 545RFE has two O/D ratios. One (.67) for cruising and one (.75) for towing. It puts the Hemi at 1800rpm towing 65mph. It doesn't take too much of a hill to make it shift out of O/D to third (direct) where it runs 2600rpm. Not that ya'll give a crumpet but the point is, if my Hemi is built and designed to two in O/D, I can't imagine the Cummins with auto not towing it's rated load in O/D. I towed heavy with all four of my Dodge/Cummins trucks in O/D. Never had any problems with the trannies sept for a governor pressure sensor in my '01.5. Not from towing, it shorted out. Then I noticed while servicing the tranny in my '03 that the wire harness for the sensor assembly was rubbing against the valve body on a sharp edge waiting to short out too. I bent the wires down to clear it for it's new owner. He's the ones shaking and vibrating now!

Hannibal.

I test drove a 2500 Hemi (3.73) pulling a 2 horse (high profile) bumper pull trailer with 1 horse in it (total weight was #4,500) and I found the truck would not hold OD at 65 MPH if there was a slight incline or any headwind. The overhead computer was showing an average of 6MPG at that speed. When it kicked out of overdrive, the rev's kicked up to the 3,000RPM range, jerking the load forward (not good for horse hauling).

I bought the 2500 with the Cummins (555 lb. ft.). I also purchased a new 25.5' Gooseneck (2 horse + living quarters) with a total weight of #7,500 loaded. I tow at 65 MPH (1,600RPM) in OD with a displayed fuel mileage of 12 - 14 MPG (lower if it is really windy). The truck almost never needs to drop out OD and it pulls my load easily.

The Hemi is a great engine, but if you need to pull a heavy load in OD, Cummins is the only way to go, unless you want to cruise at high RPM's and poor fuel mileage. Of course, it's quick in daily driving - so patience isn't necessary in daily traffic (like it is with the Cummins).

As far as this thread's topic: I agree with the others - As long as the transmission doesn't "hunt" up and down in and out of OD and you don't need to have the pedal 7/10's of the way to the floor to maintain your speed, OD is OK!

Reply Like

01-11-2005 | 06:47 PM

#32

Hannibal

Registered User

Joined: Jul 2004

Posts: 566

Likes: 0

From: west central Florida

Yep you're right. It has to be flat and calm to tow in O/D with the Hemi. Even the shorter .75 4th gear O/D in tow haul mode. Doing the math, I have to be in direct drive to make the same HP the Cummins 460 made in O/D. All that 345 Hemi HP is at 5200rpm. 200HP is around 3000rpm with the Hemi and under 2000rpm with the Cummins. I don't mind the lower mpg and higher rpm. It's quiet there and holds speed on rolling hills towing our 5th wheel. 2600rpm is nothing for the Hemi and it's actually quieter and smoother there than it is at 1800 in 4th. I'd just as soon it lock out O/D altogether for towing. I liked towing with my four Cummins powered Rams in O/D but the '03 really burned me with it's drive shaft vibrations. I was getting 10.5-12mpg with the Cummins and 8.7mpg at 65 seems to be consistant with the Hemi towing calculated miles/gallons. There's always the next truck but for now I'm not dissappointed with the Hemi in any way.

Reply Like