towing rpm

[mpaulson]

What rpm does Cummins say is a safe and best range to run the 6. 7 at while towing? I know that my old 24 valve was best in the 2100 to 2450 range on the highway as far as the torque and fuel curve went. the 6. 7 seems to run good at 2200 to 2400 also. does Cummins recomend this? they said to drive the 24 valve all day at 2400 rpm and it wouldn't hurt it. I haven't seen a fuel curve chart from Cummins on this engine like the ones available for all the other motors.

 

[HBarlow]

What rpm does Cummins say is a safe and best range to run the 6. 7 at while towing? I know that my old 24 valve was best in the 2100 to 2450 range on the highway as far as the torque and fuel curve went. the 6. 7 seems to run good at 2200 to 2400 also. does Cummins recomend this? they said to drive the 24 valve all day at 2400 rpm and it wouldn't hurt it. I haven't seen a fuel curve chart from Cummins on this engine like the ones available for all the other motors.

I found a recommendation recently for the 6. 7 engine on Cummins' website but didn't save it.



IIRC and in my words, not a direct quote, the recommendation stated that the engine is most economical at 1950 rpms and it should be operated between 1950 and 2400 rpm. The statement went on to say it was not recommended that the engine be operated in a loaded condition for long periods below 1950 rpm.



This recommendation was not specifically for a Dodge Ram application but, I assume, was intended for a 6. 7 used in a MDT or MH which would normally be heavily loaded nearly 100% of the time. Probably equivalent to one of our Rams loaded to 23,000# GCWR or beyond.



Our Rams are geared more for relaxed highway cruising at low rpms without a heavy load and normally require running in a lower gear to maintain a reasonable highway speed when towing as well as engine rpm in the band recommended by Cummins. My C&C with Aisin 6 speed is geared perfectly when in Tow/Haul mode which locks out 6th gear.

 

[donnandon]

We cruise all day towing about 13k on the highway at 65mph in 6th gear (auto) with engine rpm around 1800 (start of peak torque). I think if it were a problem, the trans would downshift? Usually the engine temp is around 200, and the trans at 160-170 if it is warm out. The only thing I knew about was not lugging the engine at full load below 1500 rpm I think, which the auto never lets happen. I think when we are on the highway, our Insight says we are at approx. 30-40% load.

 

[Simplysmn]

I run mine most of the time when towing I try to keep it close as possible to 2000/2200 thats seams to be the sweet spot for fuel economy .

 

[mpaulson]

If I run in sixth gear the load % is up around 70 to 100% all the time and I lose speed on the littlest hills, if I use 5th gear, it is around the 35 to 60% load and will climb mountains without slowing or shifting. My load is around 11,000 lbs. The egt shoot up an extra 100 degrees also. DBracy is seeing 30-40% load in sixth gear, I run 20 to 30% empty.

 

[Hoefler]

Around here where nothing is flat, I run in 5th at 55 and it is happy there in the 2000 rpm range. Out on the Interstate, running 70-75, 6th gear, 2000 rpm, will run there all day and never down shift.

 

[machinemover]

Ok So I am not really sure if you guys are talking 6-speed manual or 6-speed Automatic? I am wondering, is it ok to pull on flat interstate in automatic without the tow/haul engaged? Seems fuel economy is much better, lower RPM's. OR is this bad?

 

[Jumbo Jet]

At 70 MPH, I am running 1750 RPM in 6th (Auto)

 

[Jim W]

In July I and my DW drove to the Badlands in SD, round trip and driving around in the badlands was 2300 miles. I avg 10 MPG, I never took the truck out of tow haul mode and left the EB on all the time. In my sig you will see that I have the 6 spd auto for a 2500HD. I did regen a couple of times and my engine RPM's were keep between 1500 and 2000. I would manual shift the auto from 4 to 6 depending if we were on the interstate or not.

I feel much safer with the EB and tow haul mode on this TV then my last TV which was a 2500HD Chevy 6L gaser. I used the brakes on a vehicle very little, I rely on engine braking all the time. I learn how to drive on a stick and I was taught to use the engine to brake and then apply your brakes. So the tow haul mode and the EB are great for me. Just watch your distance and keep the RPM's in the proper torque range and you should be fine.

 

[HBarlow]

Ok So I am not really sure if you guys are talking 6-speed manual or 6-speed Automatic? I am wondering, is it ok to pull on flat interstate in automatic without the tow/haul engaged? Seems fuel economy is much better, lower RPM's. OR is this bad?

It doesn't matter whether manual or automatic. The same operating guidelines apply.



The Aisin will allow the engine to lug at 1000 rpm with a very light load and throttle. It is best to take charge and select Tow/Haul mode when towing. It also gives you the full benefit of automatic downshifting and exhaust braking.



Read my post above where I reported what I read on the Cummins website. Your gearing might be just a bit lower in your 4500 but if you run loaded in regular mode, meaning not "Tow/Haul" or "OD Off", the transmission will make softer shifts and shift up earlier and down, if at all, later. Softer shifts mean more friction and more heat transmitted to the transmission fluid. Also, in regular mode the truck will shift up to sixth gear and run at a very low engine rpm at 60 mph. Peak torque of 610 ft. lbs. begins at 1600 and continues flat to 2900 rpm with our engines so as long as you run it at or above 1600 rpm it will be producing peak torque and probably won't be damaged. However: The Cummins website stated that the most economical engine rpm is 1950 rpm. Cummins also said that the engine should be operated between 1950 and 2400 rpm. It further stated that it is not a good idea to run it at less than 1950 rpm loaded for long periods of time.



If you're towing heavy as I assume you will be, the truck will perform great in Tow/Haul mode between approximately 58 and 64 mph. Your road speed may be a little lower than mine depending on rear axle ratio.

 

[machinemover]

At 70 MPH, I am running 1750 RPM in 6th (Auto)

How did you get a 373 on your truck? I thought the best you could get with an auto was a 444?

 

[machinemover]

Well, Everybody complains about the fuel milage with these new trucks. I have 1250 miles on it, just ran about 800 miles to LA and back. I am pulling a 45' lowboy and weighing about 11,000 lbs. computer said 11 mpg, I kept the rpm's at around 2000 most of the way. My '06 3500 4x4 manual 6 would do about 9 on the same trip and half the power on the hills. I had an edge and it was basiclly worthless because the EGT's would run so high so quick you had to lay off immediatly. I am so glad I got rid of that truck.

 

[Bobcat698]

How did you get a 373 on your truck? I thought the best you could get with an auto was a 444?

Thats only true for the bigger C&C trucks, 4500-5500.

 

[EB]

I work in south Texas, mostly flat lands, very few hills. I run my 3500 cab and chassis with the Aisin transmission in drive. If it needs a gear other than 6th, I let the transmission do its own thing. I usually run 66, 67 mph and have found the fuel mileage is better in 6th than 5th. Like I said, if it needs to shift, it will shift.

 

[HBarlow]

How did you get a 373 on your truck? I thought the best you could get with an auto was a 444?

I think his truck is a pickup not a cab and chassis.

 

[BobTaylor]

Ok So I am not really sure if you guys are talking 6-speed manual or 6-speed Automatic? I am wondering, is it ok to pull on flat interstate in automatic without the tow/haul engaged? Seems fuel economy is much better, lower RPM's. OR is this bad?

I ran from Tennessee to Nova Scotia in August. I used the Tow/Haul mode on the way up, but the shifting was so rough that I took it out on the way back. Shifting is much smoother, especially on the downgrades. I told my dealer about this and he said, no problem, use it if you want or leave it off, but it will slam into gear if you use it.