Newbie here & to Dodge trucks too,
Recently purchased 2006 3500 4x4 with the 4spd auto & tow haul mode. As the truck will be used around the ranch for towing horse trailer etc I'd like to get it straight in my mind as to what exactly is happening when I place the transmission in tow haul mode. Is this a modified control program that changes the shift points only or does it also change how the lock up clutch is controlled.
How does this compare to the Allison in the GM's, I may have been under the missconseption that the converter locked up in all gears & had to be hand shifted on the Allison when in tow mode.

 

Can't speak for the Allison but this is how the 48re works.

Normal mode - shifts go like this 1-2-3-4-TC lockup.

Tow/haul mode - 1-2-3-TC lockup-4-TC lockup. 3rd seems to hold a little longer than normal mode.

Tow mode - 1-2-3-TC lockup.

Also in T/H mode trans will downshift to third when slowing down, I think somewhere around 45 mph. Also if your driving at highway speeds the trans will hold OD more than if it were in normal mode.

 

Also when you have T/H on and shift to 2 you can lock the converter up in 2.

 

Yup, it will lock in 2nd accelerating if manually shifted when in T/H or OD off mode. Will also lock in 2nd for decellerating (weak exhaust brake) if manually shifted when in T/H or OD off mode, all you have to do is blip the throttle to make the TC lockup.

As a side note the transmission will run cooler when the TC is locked. All the fluid is going to the coolers when locked vs most of the fluid dropping back into the pan without being cooled when unlocked.

 

Thanks for the replies, In tow/haul mode it operates basically the same as the auto in the old Ford powerstroke we have here but I wanted to make sure I wasn't missing something.
What advantages would there be to operating the transmission in the normal mode where it is driving on the fluid coupling of the torque converter except once it has locked up on the clutch in 4th (OD). Wouldn't this just create excess heat & increased fuel consumption when the clutch is not locked up? Does anyone know off hand what the stall speed of the stock torque converter is?

 

I like driving in normal mode for the sake that if you need a lot of throttle suddenly, the TC is going to unlock anyway, so if you're already driving unlocked that saves a step. It smoother.

Just going from feeling alone, I also believe T/H mode increases line pressure. The shifts are much firmer and TC lockup is more solid.

I think the stall speed for the stock TC is around 2200 RPM, or so I've heard around here. I went with a tighter TC with my aftermarket trans, but let me say this: I need to run a power adder now for my truck to be streetable. If I run my tight TC with stock power, it lugs really badly off the line to the point where I think it's dangerous. There's a lot of hype around here about how sloppy the stock TC is, but the bottom line is that the stock TC is a good match for stock power. If you tighten it up you need to crank up the power to match.