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Old 11-22-2015, 05:12 AM   #1
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Tow package & gas mileage

Hi.
I have a 22ft Prowler and my TV is a 2005 Dodge Dakota, 4.7 V8. My fully loaded GVW is 10440 lbs. My question is, when to use TOW. When on level road travelling at 50mph my tach reads 1800rpm . Using TOW it jumps to 2500rpm and you can almost see the fuel guage go down ! I understand that the truck has weight to pull along with wind resistance but which is harder on the truck- high rpm or cruising in [D] ? My experience as a tractor/trailer driver tells me that you pull to get up to speed then momentum alone takes pressure off the drive train.
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Old 11-22-2015, 05:53 AM   #2
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We used to have a truck with a 5.3L gas engine towing a trailer with a 5,000 GVW. I never used the Tow/Haul button.

I imagine your 4.7L gas engine is working pretty hard with a 10,440 GVW trailer. Even if your trailer is not fully loaded, I would use Tow/Haul mode most of the time. What it does is change the shift points to a higher RPM and disengage the overdrive. That's the reason for lower gas mileage, but it will be easier on the drive train. Maybe you can turn off Tow/Haul when you get up to cruising speed on the interstate, but I would run with it on most of the rest of the time in your case.
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Old 11-22-2015, 06:35 AM   #3
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You might want to think about upgrading the TV. Pulling that much weight, the 4.7 really doesn't have enough power or torque to do it.
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Old 11-22-2015, 06:54 AM   #4
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If you look back at the OP's thread in September, the 10,440 pounds is the combined weight of truck and trailer. Probably well within the manufacturer's limits.



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Old 11-22-2015, 10:54 AM   #5
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I would use tow/haul feature only to prevent unnecessary shifting to overdrive and back while going through hilly terrain . Otherwise, let your truck do its job.
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Old 11-22-2015, 02:36 PM   #6
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Quote:
Originally Posted by paz View Post
4.7L gas engine is working pretty hard with a 10,440 GVW trailer. Even if your trailer is not fully loaded, I would use Tow/Haul mode most of the time. What it does is change the shift points to a higher RPM and disengage the overdrive. That's the reason for lower gas mileage, but it will be easier on the drive train. Maybe you can turn off Tow/Haul when you get up to cruising speed on the interstate, but I would run with it on most of the rest of the time in your case.
I echo this thought by paz.

Vallance,

At slowmachines post, I read your thread where the trailer is less than 5K lbs. Even with that weight, I would use the Tow/Haul mode on the majority of the time around town and hills; and, have Tow/Haul off only at highway speed.

Safer for, and better performance from, the transmission.

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Old 11-22-2015, 03:00 PM   #7
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Use TOW until you replace the vehicle with one better suited for the job. I've heard it does more than change shift points, it changes the way the transmission works in little ways that are better for the transmission while under towing load. If your owners manual says to use it, use it.

When I use TOW, it won't shift into top gear until I'm over 60 and the strain on my engine is low enough, otherwise it stays in 5th, but it doesn't use more fuel compared to top gear at the same speed.

If you are greatly concerned about fuel mileage while towing, you are in the wrong hobby IMO.
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Old 11-22-2015, 05:08 PM   #8
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Quote:
Originally Posted by Vallance View Post
I have a 22ft Prowler and my TV is a 2005 Dodge Dakota, 4.7 V8. My fully loaded GVW is 10440 lbs.
4.7L V-8 and five-speed automatic 3.55 axle ratio:
Payload 1,536 lbs.
Towing capacity 4,450 lbs.
GCWR 9,200 lbs.

Quote:
My question is, when to use TOW.
10,400 actual gross combined weight (GCW) compared to the 9,200 pounds GCWR of the truck means you're 1,200 pounds over the GCWR of your truck. Overloaded!

That means you probably struggle on steep grades (hills, mountain passes, even tall overpasses) and your drivetrain needs all the help it can get to tow that much overloaded. You're probably the slowpoke holding up traffic when climbing steep hills and passes. So use Tow/haul mode all the time when towing that heavy.

If your wet and loaded tow vehicle (TV) without the trailer weighs more than (9,200 minus 4,450 =) 4,750 pounds on a CAT scale, then you have even less than 4,450 pounds tow rating. So when towing that trailer, watch the coolant temp and tranny temp gauges like a hawk. Never allow more than 225 tranny temp, else your automagic tranny will have a short life.

Quote:
My experience as a tractor/trailer driver tells me that you pull to get up to speed then momentum alone takes pressure off the drive train.
But does your commercial trucker experience include hauling loads that were 11% or 12% more combined weight than your tractor was rated to tow? Maybe if you were driving the bosses' tractor, but I'll bet not not if you were a successful owner/operator.
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Old 11-23-2015, 03:59 AM   #9
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Heat is the transmission's nemesis, and each time a tranny shifts it generates heat. With the shift points changed while in TOW mode, the chances of shifting gears while going down the highway are reduced.
Even while on a seemingly flat stretch of highway, a good wind can cause your loaded vehicle to have to downshift to maintain momentum.
You can add another item to the watch list while driving and keep a diligent eye on the tranny temp and kick on the TOW mode when you see the temp increase because of excessive shifting, or just leave it in TOW mode and enjoy the ride.

Myself, I'm tugging a hefty load down the highway, so I just accept the fact my gas mileage is not going to compete with my wife's Hyundai.

Some people like to gamble. Some people are lucky. The way I see it, pay at the pump, or pay at the tranny shop.
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Old 11-23-2015, 05:21 AM   #10
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Thanks for advice. Slowmachine, you found my earlier post.Thanks for clarifying my total weight,truck & trailer, is 10440 lbs. I should be OK but I have yet to pull any significant hills....
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