I don't know about running at "3k all year long". I ran my 06 bobtail from sacramento ca to salmon id at around 2500rpm because I was in a hurry and used almost 3/4 of a gallon of oil in 1600 miles. on the way back I ran 2100rpm and didn't use a drop. they will run those high rpm's but they don't like it. I think 17 to 22 is the proper towing range and 2000 or less if you want mileage.

 

Ok, so here is a question for you. I have 3.55 gears. At 62 mph (100 km/h) I'm at either 1650 rpm in o/d or 2,400 rpm in drive. I tow a 26 foot TT and it will pull it in o/d and I do get decent fuel economy (16 mpg), but it seems likes its lugging slightly. Should I just let her rev at 2,400 rpm and put up with the noise? In order to pull 1,900 rpm in o/d I'd have to be doing close to 80 mph which makes the wife a little nervous towing the trailer that fast. I'd love to have 3.73 gears with my lower hp motor, but cannot justify spending that much cash

 

2-2500 seems to work the best for me. I don't worry about the speed as much as I do the rpm's.

 

Agreed!
Haven't seen it posted in a few yrs but I remember reading where Cummins regularly tests their engines at 3000 rpm for 1,000 hrs (?) non stop!
Anyone remember the specifics?

RJ

 

I would hope they would because the same powerplant goes in gen racks too. Full throttle for hours on end unless you have blowby problems and then you're going to start using oil.

 

For those of you that have 5.9's, consider that the Marine Application for the 5.9 in a generator set is rated for 14,500 hrs at 1800rpms. That is a bunch of hours.

As far as what speed to tow at or RPM's, the torque curve of the 5.9 extends from the low point to about 2700 rpms with not much change in value. So I don't think you will be lugging the engine much in the torque range.

The Transmission is another story. If your running with a NV5600 or G56 It don't matter. If its a mush box, you need to watch the temps and figure out
where it runs the coolist at. (Temp Guage)

Find a ventilated extra capacity Tranny pan and install it. You can drain it from the pan and there is a fitting for a temp probe in the pan. About 235 bucks on line.

Dave

 

Put taller tires on it. The taller the tire the more it will lower your rpm's. I realize we have different tranny's, but i managed to get mine down to almost 2000 rpm from 2300 rpm at 75 just by going from 265's up to 285's.

 

Anywhere between 2100/65mph and 2250/70mph. Craig

 

I too try to tow at around 2000 rpm, my problem is speed, I'm always going faster than I should. Only speeding ticket I've had was with my trailer, the officer said I should have racing stipes and a number.

 

I set it at 62 to 65 miles per hr and get good mileage at that speed.My total weight is 22.900+ my mileage from In to Ca and back was 14.2 That was around 7000 miles from last winter trip. I am a snowbird. You can play with your speed and you will find a sweet spot that your truck will get good fuel mileage==Good luck

 

I like driving 65 but the speed limit is 55 on the back roads here. 70 seams to be the best for pulling hills witha big load on the trailer.

 

Sounds like you need more goodies!

 

One thing to remember is torque gets the load moving. HP keeps it moving. At 1600 rpm (max TQ) there is not much HP. I find pulling my 8k loaded enclosed car hauler at 1600-1700 rpm in OD the engine sounds like it's lugging. 1800-2000 rpm is perfect. I recall reading on Cummins web page they say the torque drops off slowly after 1600rpm but the HP comes up quickly. They say the best combination for TQ and HP is around 2300-2500 (if I remember correctly). If your pulling really heavy I would think you want to be in this rpm range (using whatever gear gets you there). Cummins also defines lugging as pushing on the go pedal and the engine does not increase rpm. If this happens you need to drop a gear.