rpm when towing

rhagfo wrote:

4x4ord wrote:

VoodooMedicineMan wrote:
Next time I am going to try that. 3300 seems awful high.

There is nothing really wrong with what your doing it just means that you will go slower up the hill. Anyway the way to maximize your speed up a long hill is to start by anticipating the hill. By that I mean downshift before the truck begins to slow down.

So if you are going 60 mph in high gear with 3.73 gears your engine will be turning about 1713 rpm. Drop two gears and you should be travelling 60 mph and revving 3117 rpm. If the truck is pulling a long steep hill it can slow all the way down to 42 mph before you can shift again. At 42 mph your engine will be revving 2183 before the shift and 3500 after the shift.

Well don't know the listed red line on the Cornbinder 6.0. but 3,300 rpm would be 100 rpm over my CTD 5.9's red line.
I don't like taking it much above 2,500 as that seems to be the point power flattens out.

Thats cause the Cummins is most at home at 2100rpm. Peak torque. Everyone gets caught up in the HP craze. Horsepower doesnt do crapola for pullimg grades. Gear it for peak torque and let it pull.

What you're feeling drop off at 2500 rpm is the torque. The engine is still building HP till 2700 rpm. Exactly how much over 2700 before power drops off significantly I don't know. There is likely useable power till 3000.

So if you shift at 2500 where you feel the torque drop off you miss out on the peak hp.

Think of it like this: you are accelerating with foot to the floor in 3rd gear, at 2500 rpm you feel in the seat of your pants the engine seems to stop pulling hard so you shift to forth. Your rpms drop to 1450 which is very close to peak engine torque but you lost the torque multiplication of third gear so your rear wheel torque dropped off more than had you continued to rev your engine to 2900 - 3000 before shifting. To use your engine's full power you will use some rpm beyond the peak hp rpm.

Redwoodcamper wrote:

Turtle n Peeps wrote:
Put the thing in TH and drive. Forget about shifting and trying to out guess a computer.

If someone has an aisin, then the above advice is great. But with the stock 68rfe it will bog down to 1100-1200 Rpms at 50-70 percent throttle and not downshift. Egts go crazy, tranny clutches get cooked. Companies tune things with mileage and the EPA too close in mind. So many posts on here from people who have never driven or towed with a 68rfe. Let alone tear one apart or have to rebuild one. Which I have done. It isn't a bad tranny, just has some weak points.

Agree, in normal mode, but my experience with the 68 in tow mode is it gets rid of that laggy lugging gear change. Although a trans tune for the 68 is money well spent imo. It just don't shift as well as the other 3 auto trans.

4x4ord wrote:

VoodooMedicineMan wrote:
Next time I am going to try that. 3300 seems awful high.

There is nothing really wrong with what your doing it just means that you will go slower up the hill. Anyway the way to maximize your speed up a long hill is to start by anticipating the hill. By that I mean downshift before the truck begins to slow down.

So if you are going 60 mph in high gear with 3.73 gears your engine will be turning about 1713 rpm. Drop two gears and you should be travelling 60 mph and revving 3117 rpm. If the truck is pulling a long steep hill it can slow all the way down to 42 mph before you can shift again. At 42 mph your engine will be revving 2183 before the shift and 3500 after the shift.

Well don't know the listed red line on the Cornbinder 6.0. but 3,300 rpm would be 100 rpm over my CTD 5.9's red line.
I don't like taking it much above 2,500 as that seems to be the point power flattens out.

Turtle n Peeps wrote:
Put the thing in TH and drive. Forget about shifting and trying to out guess a computer.

If someone has an aisin, then the above advice is great. But with the stock 68rfe it will bog down to 1100-1200 Rpms at 50-70 percent throttle and not downshift. Egts go crazy, tranny clutches get cooked. Companies tune things with mileage and the EPA too close in mind. So many posts on here from people who have never driven or towed with a 68rfe. Let alone tear one apart or have to rebuild one. Which I have done. It isn't a bad tranny, just has some weak points.

Redwoodcamper wrote:
If you have the aisin tranny, then that is correct. 68rfe is different. There are hundreds of tranny rebuilds because of that thinking.

What is correct?

and "what" thinking?

Your post doesn't define what previous post you are referring to.

2015 Ram/Cummins here.
Engage TH and EB
Lock out 6th gear and let her rip!
At 65 mph I'm right in the sweet spot of 1800-2000 rpm.
Nothing like it just pulling like a freight train and that diesel humming along!

VoodooMedicineMan wrote:
Next time I am going to try that. 3300 seems awful high.

There is nothing really wrong with what your doing it just means that you will go slower up the hill. Anyway the way to maximize your speed up a long hill is to start by anticipating the hill. By that I mean downshift before the truck begins to slow down.

So if you are going 60 mph in high gear with 3.73 gears your engine will be turning about 1713 rpm. Drop two gears and you should be travelling 60 mph and revving 3117 rpm. If the truck is pulling a long steep hill it can slow all the way down to 42 mph before you can shift again. At 42 mph your engine will be revving 2183 before the shift and 3500 after the shift.

RCMAN46 wrote:
With my Duramax / Allison I put it in TH and never have to worry about the RPM up or down hill.

You got an exhaust brake?

With my Duramax / Allison I put it in TH and never have to worry about the RPM up or down hill.