Heavy Hauling Question

[jwynnejr1]

Need some input from you guys who haul often. I had a gooseneck hooked to my truck last week and the total load (including trailer) was around 15/16k. It pulled it fine except for a few times going up some steep-ish hills. Going up the hill it would maintain speed, but not accelerate or downshift. Turbo gauge showed increase in pressure.

Can this be contributed to the wonderful transmission tuning that we have in these trucks?

2018 Ram 2500
3.42 gears
6.7 Cummins

 

[jwynnejr1]

I should add, I've experienced the same type of condition hauling my ranger (probably less than 5k total weight) on the bumper. It pulls it fine, but when I lean into the throttle it doesn't downshift. It just keeps accelerating (slowly) in that same gear.

 

[HDGoose]

Hhmmm...I never experienced that pulling my 12k 5th wheel up some two lane roads in WV/NC/TN mountains. My truck was a 2013 Ram 2500 Tradesman Diesel CC SB 4x4 3.73. It would shift and pull uphill Just fine.

 

[jwynnejr1]

Hhmmm...I never experienced that pulling my 12k 5th wheel up some two lane roads in WV/NC/TN mountains. My truck was a 2013 Ram 2500 Tradesman Diesel CC SB 4x4 3.73. It would shift and pull uphill Just fine.

Did it have the 68RFE transmission?

 

[HDGoose]

Did it have the 68RFE transmission?

Yes on the 68RFE automatic 6 speed. And trying to remember back to then, there was an update that the dealer did when another recall was done. It had to do with shift points while towing, and when I mentioned I pull a 5th wheel trailer he added it to the list of items to be done. I do nothave that truck and those paper went with the truck.

 

[jwynnejr1]

Yes on the 68RFE automatic 6 speed. And trying to remember back to then, there was an update that the dealer did when another recall was done. It had to do with shift points while towing, and when I mentioned I pull a 5th wheel trailer he added it to the list of items to be done. I do nothave that truck and those paper went with the truck.

I wish it was a more common issue. I have always chalked it up to torque management. When it wouldn't downshift running up the hill last weekend, I thought it may be more than that. Do you lock out sixth gear when towing?

 

[HDGoose]

I wish it was a more common issue. I have always chalked it up to torque management. When it wouldn't downshift running up the hill last weekend, I thought it may be more than that. Do you lock out sixth gear when towing?

I never had a need to do that. And anytime I put my foot in it it ran up hill. First trip, camper loaded to 11,500 (weighed on scale) with 3 people in truck had a grade (do not recall how much but not extreme) and decided to step on it. Truck down shifted, accelerated smoothly and quicker than I expected to 90 MPH. Wife just looked at me a grinned. Her camper,my truck.

 

[62Blazer]

What speed and RPM was the truck running prior to trying to accelerate or giving it more throttle? One thing you have to keep in mind is that the transmission will only downshift if it will not make the engine over rev. For example, if the truck is already down in 4th gear it will not downshift if the engine is already running in the 2,000-2,200 rpm range. If in 5th it will not downshift if it is already in the 2,400 rpm range.....simply because downshifting a gear would make the engine go over the redline.

 

[crash68]

^^^ what he said
Your towing with a diesel, torque does the work not horsepower. The engine doesn't need rev up like a gasser. If you were losing speed that would be cause for concern.
Do you have the Tow/Haul mode on?

 

[jwynnejr1]

What speed and RPM was the truck running prior to trying to accelerate or giving it more throttle? One thing you have to keep in mind is that the transmission will only downshift if it will not make the engine over rev. For example, if the truck is already down in 4th gear it will not downshift if the engine is already running in the 2,000-2,200 rpm range. If in 5th it will not downshift if it is already in the 2,400 rpm range.....simply because downshifting a gear would make the engine go over the redline.

I want to say that it was in the 2-3k rpm range. It concerned me because no matter how hard I stomp down at that point, it does not accelerate any noticeable amount. I'd like to believe I could pass someone going up hill with a load if I wanted to. It would not have happened with this one.

 

[jwynnejr1]

^^^ what he said
Your towing with a diesel, torque does the work not horsepower. The engine doesn't need rev up like a gasser. If you were losing speed that would be cause for concern.
Do you have the Tow/Haul mode on?

I'm not losing speed, but I'm not gaining either. I do have tow/haul on.

 

[62Blazer]

I want to say that it was in the 2-3k rpm range. It concerned me because no matter how hard I stomp down at that point, it does not accelerate any noticeable amount. I'd like to believe I could pass someone going up hill with a load if I wanted to. It would not have happened with this one.

At some point in time you are simply going to run out of power and not have the ability to accelerate up a hill. Obviously takes more power to accelerate than to maintain a steady speed, and the faster you go the more power it takes. As I said before, if the engine is already in the 3,000 rpm range it won't downshift because if it did it would force the engine to over rev.
To be honest it almost sounds like you are expecting too much out of the truck to be able to pass somebody at highway speeds, up a hill, while towing a 16k lbs. trailer.

 

[stevenP]

My fifth wheel is in the 15K pounds range pretty solidly. I how ever , have the aisin tranny in my 3500. Now I will also say I dont have a lot of hills around where I have been towing, but my truck downshifts and howls like a banshee when needed in tow haul, and with cruise engaged.

Now on my 2500 it has the 68RFE, and I havent really towed much of anything with it. It tends to just want to grunt rather than down shift.

 

[Josh Gibson]

Do you have a gear shift on your column? On my shiftier there is an arrow up and down have you tired to manually change the gear? Also have you tried feathering off the gas and see if it drops gears then slowly come back on the throttle?

 

[jwynnejr1]

At some point in time you are simply going to run out of power and not have the ability to accelerate up a hill. Obviously takes more power to accelerate than to maintain a steady speed, and the faster you go the more power it takes. As I said before, if the engine is already in the 3,000 rpm range it won't downshift because if it did it would force the engine to over rev.
To be honest it almost sounds like you are expecting too much out of the truck to be able to pass somebody at highway speeds, up a hill, while towing a 16k lbs. trailer.

I would agree with you about expecting too much, but it seems to do the same type of thing when I'm hauling my ranger on a 14 ft tandem trailer. I can floor it and it will accelerate, but not downshift. This is at about 50/55 mph and not high rpms.

 

[jwynnejr1]

Do you have a gear shift on your column? On my shiftier there is an arrow up and down have you tired to manually change the gear? Also have you tried feathering off the gas and see if it drops gears then slowly come back on the throttle?

I have tried feathering off the accelerator. Don't want to do too much of that with a heavy load going up hill though. I have the ability to lock out gears on my gearshifter, but have not tried that.

 

[jwynnejr1]

My fifth wheel is in the 15K pounds range pretty solidly. I how ever , have the aisin tranny in my 3500. Now I will also say I dont have a lot of hills around where I have been towing, but my truck downshifts and howls like a banshee when needed in tow haul, and with cruise engaged.

Now on my 2500 it has the 68RFE, and I havent really towed much of anything with it. It tends to just want to grunt rather than down shift.

A friend of mine told me it sounds like I need a bigger truck. I am almost in agreement with him.

 

[jwynnejr1]

When I experienced this condition, I also had the exhaust brake system on. I don't think that would make much difference though.

 

[mopar_man72]

I drove big rigs for 8 years. One thing that I hated to see was someone out in the left lane on a hill because he could maintain 2MPH faster then the guy in front of him. Even the big trucks run out of power on hills under heavy loads. If I had to drop a gear it didn't get me up the hill any faster, and I would have to let the RPMs come down to about 1500-1700 to safely shift (no synchronizers). I wouldn't worry about passing on the hills unless the person in front is running under the speed limit.

 

[mtofell]

One thing that I hated to see was someone out in the left lane on a hill because he could maintain 2MPH faster then the guy in front of him.

I'm glad to hear a big rig driver frown on this. Around here (Oregon) I regularly see big trucks doing this exact thing and it's terrible. Single trailer guy that can go 38MPH pulls out to pass double trailer guy that is going 35MPH on a hill. I just drove up through the mountains in southern Oregon and encountered this numerous times. Totally dangerous but happens regularly.