Engine RPMs.

muzupan · Jul 1, 2017

To all the Cummins tow masters: I have a 2016 Ram CC 2500 with a 6.7 Cummins and I now pull a Jayco trailer which is 37 feet long and about 10,200 fully pounds loaded. My engine RPMs at 63, 64 mph is in the neighborhood of 1400 to 1500 RPMs. I do not have an issue with the engine lugging so where do you like your rpm range to be when you're towing?

69GWC · Jul 1, 2017

What gear are you towing in.

muzupan · Jul 1, 2017

69GWC said:
What gear are you towing in.

6th gear.

69GWC · Jul 1, 2017

Myself I would not tow in 6th I would tow in 5th.
6th gear is a overdrive gear and its not going to like tow long term even harder on it with 3:42 gears

muzupan · Jul 1, 2017

69GWC said:
Myself I would not tow in 6th I would tow in 5th.
6th gear is a overdrive gear and its not going to like tow long term even harder on it with 3:42 gears

I will be towing again in a couple weeks and I will have to try it in 5th gear and see how it does. I know in 6th gear I have no issues.

Mega-Hemi · Jul 1, 2017

I leave it in 6th towing my 5th wheel. Weighs about the same as yours loaded. If I get in the hills where it starts lugging I'll lock out 6th.

69GWC · Jul 1, 2017

You guys know towing that heavy in overdrive is going to burn out your overdrive clutches.

BossHogg · Jul 1, 2017

69GWC said:
Myself I would not tow in 6th I would tow in 5th.
6th gear is a overdrive gear and its not going to like tow long term even harder on it with 3:42 gears

I beleive 5th is also an overdrive gear in the 68RFE.

69GWC said:
You guys know towing that heavy in overdrive is going to burn out your overdrive clutches.

I though the threat of burning the overdrive clutch was only during an engine lugging event, a difficult event to cause because the computer will force a downshift long before the lugging starts. In this context, lugging is a loss of RPMs while the throttle is wide open, like pulling heavy up a mountain.

Please elaborate, I don't have first-hand experance (don't want it either) but have read about this issue and don't fully understand it.

OP
Cummins makes just the software app you need. The Cummins PowerSpec application will tell you the best gearing and engine RPMs for your load and towing environment. Best of all it is free;
https://cumminsengines.com/powerspec-download

If you don't feel like going through all the work, I can tell you what I got. I'm pulling about 15K in a 3500 SRW with the same driveline as you. The PowerSpec said the best engine RPM is 1,800 to 2,200 RPMs. At your speeds, I use fifth gear. Actually I use tow/haul mode which keeps the transmission in fifth gear at these speeds. Hope this helps.

69GWC · Jul 1, 2017

Yes Sir 5th is as well I was told it was stronger then 6th, problem is over time its going to take out the clutches as well as heat up the converter.
From my experience with the Cummins and that trans is unless its been retuned it dont down shift soon enough.
When I traded mine off the converter was going out , just trying to help they are alot of money to rebuild.

muzupan · Jul 1, 2017

BossHogg said:
I beleive 5th is also an overdrive gear in the 68RFE.

I though the threat of burning the overdrive clutch was only during an engine lugging event, a difficult event to cause because the computer will force a downshift long before the lugging starts. In this context, lugging is a loss of RPMs while the throttle is wide open, like pulling heavy up a mountain.

Please elaborate, I don't have first-hand experance (don't want it either) but have read about this issue and don't fully understand it.

OP
Cummins makes just the software app you need. The Cummins PowerSpec application will tell you the best gearing and engine RPMs for your load and towing environment. Best of all it is free;
https://cumminsengines.com/powerspec-download

If you don't feel like going through all the work, I can tell you what I got. I'm pulling about 15K in a 3500 SRW with the same driveline as you. The PowerSpec said the best engine RPM is 1,800 to 2,200 RPMs. At your speeds, I use fifth gear. Actually I use tow/haul mode which keeps the transmission in fifth gear at these speeds. Hope this helps.

Thanks, I will check that out tomorrow on my computer.

muzupan · Jul 2, 2017

BossHogg said:
I beleive 5th is also an overdrive gear in the 68RFE.

I though the threat of burning the overdrive clutch was only during an engine lugging event, a difficult event to cause because the computer will force a downshift long before the lugging starts. In this context, lugging is a loss of RPMs while the throttle is wide open, like pulling heavy up a mountain.

Please elaborate, I don't have first-hand experance (don't want it either) but have read about this issue and don't fully understand it.

OP
Cummins makes just the software app you need. The Cummins PowerSpec application will tell you the best gearing and engine RPMs for your load and towing environment. Best of all it is free;
https://cumminsengines.com/powerspec-download

If you don't feel like going through all the work, I can tell you what I got. I'm pulling about 15K in a 3500 SRW with the same driveline as you. The PowerSpec said the best engine RPM is 1,800 to 2,200 RPMs. At your speeds, I use fifth gear. Actually I use tow/haul mode which keeps the transmission in fifth gear at these speeds. Hope this helps.

Well apparently theCummins power spec tool will not work on my windows 10 computer so I will just tried towing in fifth gear

BossHogg · Jul 2, 2017

69GWC said:
Yes Sir 5th is as well I was told it was stronger then 6th, problem is over time its going to take out the clutches as well as heat up the converter.
From my experience with the Cummins and that trans is unless its been retuned it dont down shift soon enough.
When I traded mine off the converter was going out , just trying to help they are alot of money to rebuild.

I'm wondering if the confusion, mine, in particular, is due to software versions on the trucks. For example, this spring I went to the dealer for a tire rotation, while there, they updated several ECMs including engine and transmission. The explanations were customer satisfaction, that is all they would say.

My truck has the latest software (as of May 2017) and the transmission, in fact, the entire driveline performs beautifully while pulling 15K or running empty. I don't experience any of the issues I read about and I can only conclude it is software versions that make the difference. RAM must be continually working out the software shortcomings and evolving their control algorithms.

You know how long it takes for Internet stories and rumors to die out, look at poor Ford, they are still paying for the Powerstroke mistakes 10 plus years ago on the Internet.

BossHogg · Jul 2, 2017

muzupan said:
Well apparently theCummins power spec tool will not work on my windows 10 computer so I will just tried towing in fifth gear

I ran a quick test last year, we were running on flat roads with little wind in Michigan's thumb at 60 MPH. I towed a while in sixth (tow/haul off) and then in fifth gear (tow/haul on) watching my MPG. Best I could tell it was the same and that was what I expected from reading the results other folks have posted.

It made sense to tow so the engine RPMs were in the powerband and like I said, I let the computers pick out the gears using tow/haul. Like I mentioned in post #12, my truck has the latest software in all the ECUs and I have to assume that makes the difference between my observations and all the horror stories I read about.

Mega-Hemi · Jul 2, 2017

BossHogg said:
I ran a quick test last year, we were running on flat roads with little wind in Michigan's thumb at 60 MPH. I towed a while in sixth (tow/haul off) and then in fifth gear (tow/haul on) watching my MPG. Best I could tell it was the same and that was what I expected from reading the results other folks have posted.

It made sense to tow so the engine RPMs were in the powerband and like I said, I let the computers pick out the gears using tow/haul. Like I mentioned in post #12, my truck has the latest software in all the ECUs and I have to assume that makes the difference between my observations and all the horror stories I read about.

What year is your truck? I run tow/haul in mine while towing but it just changes the shift points. Doesn't lock out 6th. I have to do that with the button on the shift lever.

BossHogg · Jul 2, 2017

Mega-Hemi said:
What year is your truck? I run tow/haul in mine while towing but it just changes the shift points. Doesn't lock out 6th. I have to do that with the button on the shift lever.

2015.

I never said tow/haul will lock out 6th. Tow/haul will not allow 6th until speed reaches mid-60s.

Engine RPMs.

muzupan

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