Safe towing rpm
 

Im planning a trip in about 3 weeks. I will be towing about 7000# 1850 miles with my 00. I plan on trying to keep it in 4th @ about 2700-3000 rpm. Is 3000 rpm safe. I have 225000 miles on it and just did oil and a new fuel filter. I will be installing boost and pyro gauges in the truck before the trip.

I used to own a 2001 2500 4X4 with the NV 4500 and towed a 36ft 5ver at around 13k, I did have boost, EGT and fuel pressure gauges but mostly kept it in 5th at around 2100rpm unless in the mountains, steep hills or strong head winds, I just watched the EGT and didn't lug the engine.

Im concerned about destroying 5th as i cant afford a replacement transmission. I know the truck was babied before i bought it. If i can reliably pull in 5th, i will but only through the Dakotas unless the wind picks up.

I owned that truck from new for 10 years and never babied but drove it hard changed all the oils with full synthetics including the power steering oil which makes a big difference if you live in the cold. I can't think of a single problem except for the fuel pressure gauge giving up the ghost and after letting me down once I changed out both batteries after around 7 years. I also installed a PAC Brake with on-board air which I really liked and was great in the mountains. I forgot about the leaky evaporator core.

I am thinking that driving at a constant 3,000RPM will drive you crazy long before you did any harm to the motor. I just pulled our 13,000lb RV from BC to Alberta through and over the Rocky Mountains Rogers Pass (Trans Canada HWY 1). I have a 47RE autotragic and a 3.55 rear end. I tow in 4th/OD on the flats at around 1,700RPM. In the mountains I kick off the OD and let the motor rev in 3rd with the TC locked up and keep an eye on the EGT's. RPM's will climb right up to 2,750 to 3,000 depending on speed.. If temps, any of them, get too high, I slow right down, shift to 2nd and keep the RPM's around 2,250 RPM's. I tried a long tow once with the OD off for an extended period. At a constant 2,500RPM the drone/roar of the motor was just too much for me to handle so I turned the OD back on and let the RPM's drop to a more audibly pleasing level. Temps usually stay well within normal parameters while towing with OD on.

Cheers!

Mike

Many years ago I asked a Cummins Engineer how many RMP's were too much and his reply is that if the governor didn't cut in you weren't revving it to high, but that you could run against the governor without harm. Like was said, not sure you want to listen to it that way though.

The big problem with 5th is lugging it down below 1500rpm. Best bet, if rpm drops below 1800, drop a gear till you get past the hill the upshift. 7000# shouldn't be a problem for you...

That makes me feel better about 5th. I will use it when i can, and ill also let you all know how bad the 3000 rpm drone is while im in the hills in Montana

Ok so i made it to Montana about a weeks ago. Did between 65 and 80 the whole way.There was no real issues other than i have to replace my pinion seal and figure out where all the oil is coming from on the engine. I got roughly 10mpg the whole way, but i contribute that to the high speeds. Egts never went over 900 and i did max my boost around 28 psi on the hills (i need more boost i think).

Well said-GOOD ADVICE
7000 is not that much weight fear not

You are towing at 3000 rpm?

What is your egt?

Oil is coming out breather at front of engine....

I actually e mailed Cummins about RPM of the 5.9.

Basically the reply was to avoid lugging the engine, which they defined as running the engine with a load below 1600 rpm, or running the engine where full accelerator does not accelerate the vehicle.

On the top end they related the 3150 governed engine speed was Safe, and not to allow engine braking to exceed governed rpm. Also that power peaks at 2750, so although Safe there is nothing to gain by running above that, other than higher road speed in a given gear.

I actually never went over 2500 rpm. I did drive in 5th and the truck didnt care. I did have to drop to 3rd though on I-90 going into Butte MT, and then again driving in the Mission Valley on U.S. 93. Egts never went above 900. It was a fun trip, just cost more in fuel that I was hopeing. After crossing a CAT scale, the trailer was 8500#. I think the tr7ck would have done fine towing twice as much weight.

When I had my '98 12v with a NV4500, I towed our 10,000# 5th whl all over the U.S. using 5th gear on near flat roads. The only problem I had, twice, was that the nut that holds the 5th gear came loose, which renders a 5 speed to a 4 speed. Fortunately I had US Gear overdrive and was able to tow in 4th over, which was about the same ratio.
John