Tow Haul question

[AlFischer]

Towing aprx 10k travel trailer on a long flat hwy at 55-60 mph. My understanding is when using tow haul that fuel mileage goes down a bit. Is there any advantage to using tow haul under this condition? Would turning tow haul off cause any problem? Hwy 5 in Calif is an example of over 100 miles of flat road.

 

[Gonzo 1066]

The only thing that Tow Haul does is modify shift points to a higher RPM and make the shift a bit more positive. The gear ratios stay exactly the same. I dont think that you will see any appreciable difference in MPG in or out of tow haul,

 

[AlFischer]

OK. I will just leave it in tow haul and EB on while towing. I was thinking it might leave it in lower gear. (always looking at saving a bit of fuel)

 

[RikDavis]

At 55 mph it is sort of a toss up between 6th or locking it in fifth.. On hilly roads I tend to prefer fifth. on the flat 6th seems to be ok.
Tow haul should not have any affect on fuel mileage at steady speeds.
When not in tow haul running empty I think it shifts to 6th way to soon and you can feel the engine is lugging

 

[RVTRKN]

What rear diff ratio do you have? If it's 3:42 or 3:73, I would turn on tow/haul while on flat runs. I'm very familiar with that route, but to know if you save fuel, would be to hand calc different auto settings to see. You could use your overhead, but then all comparisons would require you use that.

 

[Joseph Donnelly]

Ram recommended to me using tow/haul when pulling a trailer, but it may not be needed with just a load in the bed. I think you would onlyu see a slight mpg difference, and that would be solo driving.

 

[AlFischer]

I am not sure which differential. "THINK" it is 3.73. I can notice some lugging when driving around town, The tach shows about 1000 which seems pretty low.

How can I lock it in 5th or 6th?

Only have abt 3k on the truck, mostly towing and LOVE it. (except for being too tall) Hard for 73 yr old Al to climb in! Just starting to watch MPG and have no calced it yet. Overhead says 13-14 towing depending on my right foot and attitude! Good ride, great power and QUIET! ( had a 2001)

 

[Cummins12V98]

I hit TH and EB every time I start the truck. Can't strand the pre mature shifting and lugging.

On the shifter there is a switch, you will figure it out!

 

[Cummins12V98]

I run I-5 a lot. I tow at 60-62 and on flat land to small hills it stays in 6th. Anything more I lock in 5th. I have 3:42's and 28K combined load.

 

[AlFischer]

I'm going to have to remember to hit TH and EB at every start. The premature shift doesn't really bother me but lugging has always been a no-no. Wish it could be set to default. Haven't seen ice in Fresno for a loooong time!

Looks like I was too concerned about fuel mileage. Not much difference.

 

[tmcIlwain]

I think one of the best reasons to use TH with the EB is the owners manual statement:


The automatic transmission will downshift more aggressively
in TOW/HAUL mode when the exhaust brake is
enabled to increase brake performance.


Tom

 

[RikDavis]

I think one of the best reasons to use TH with the EB is the owners manual statement:


The automatic transmission will downshift more aggressively
in TOW/HAUL mode when the exhaust brake is
enabled to increase brake performance.


Tom

Also, at least on the 13 a second push on the EB button puts it into "smart brake" and it will stay on and downshift also if the EB isn't enough. On my WV trip I think the combination downshifted more going downhill than I did going up the hills

 

[Too Tall]

Towing aprx 10k travel trailer on a long flat hwy at 55-60 mph. My understanding is when using tow haul that fuel mileage goes down a bit. Is there any advantage to using tow haul under this condition? Would turning tow haul off cause any problem? Hwy 5 in Calif is an example of over 100 miles of flat road.

The truck has 6 gears regardless of in tow haul or not. As mentioned the shift pattern is changed. If you have the 3.42, you are going to be at about 11 -1200 rpms. At that speed and rpm, you'll probably be in 5th gear. On my truck, I shut off tow haul and the transmission will shift to 6th. Then, I put back in tow haul and it will stay in 6th as long as you can maintain 1200 and speed. You'll get better mileage and still have all the advantages of tow haul. Just kind of faking it out to run in 6th for the better gas mileage. Don't worry about lugging because it's smart enough to drop down to 5th if it needs to. This works well for me and gives me about 1 mpg better mileage.

 

[RVTRKN]

I don't have a newer truck, but I'm willing to bet the owners manual recommends turning on T/H when heavy, it can take out a trans. It even can take out a manual trans (NV5600) if you don't run in 5th as the manual recommends, when heavy. I would shift to 5th at the first sign of an incline and back to 6th on down hill runs and slight down hill runs.

 

[Too Tall]

Agree, that's what tow haul is for, towing. However, the shift point and quicker lock up is the only difference, so as lone as you are locked up, it doesn't matter which gear you are in.