thats just what i was about to ask.

when someone answers this can you do it like so:

O/D Off: blah blah blah

Tow/Haul: blah blah blah

thanks! lol.

 

the way the book reads it changes shift points when you have either one on.
o/d off prevents it from shifting into 4th or 5th
tow/haul prevents it from shifting into 5th

 

Use tow/haul anytime you like. It is great in city traffic towing or not. It will delay the shifts and give you more performance.

 

yes, just rememeber to turn it off when freeway drivin.

I used it when drivin cross country for work on up and down grade.

 

For the 545RFE trans, tow/haul will not allow it to shift higher than 3rd gear.

4th and 5th are overdrive.

And, I have proven this on the dyno with my 04 that says Tow/Haul on the shifter lever.

 

I have an 06 Power Wagon (2500, 5.7L LOVE IT ) and it was an open trailer. I can't be positive but I'm not sure how accurate the statement about not shifting past 3rd gear is. From Sac to Pismo (read all freeway) my rpm was around 2500 at 55 mph which, to me, sounds like 4th gear. I could be wrong and I'm out of the country now so won't be able to verify.

I have both settings on the PW, O/D off as well as tow/haul but only one at a time. T/H and O/D off most definitely are two seperate beasts, but I wouldn't be able to explain the difference other than what I've said. I don't claim to be a mechanic, just joe blow with a little driving experience but T/H provided more consistant, smooth shifting and changed shifting points and O/D off just seemed to be normal driving setting minus that final drop in RPM requiring an upshift for any power.

As I said, I was highly impressed. Many somewhat steep hills, I expected the tranny to upshift with cruise control set and it just powered right up them, not even skipping a beat and without the slightest drop in speed. Then on the downhill side where I would expect the old chevy to run away on me, the PW would upshift for an engine brake. It was incredible. I can't say it enough, I love that thing. Best truck I've ever owned. Not even to mention it's performance in the dunes ... The winch was impressive. The largest setup I pulled out was a 1 ton chevy with a triple axle 5th wheel.

 

OD off is just that. It turns overdrive off.
Tow/Haul actually electronically alters the shift points as well as preventing the trans from shifting into OD.

Pulling a 5K pound boat with my 2500 Hemi I get 1mpg better on the highway at 70mph in Tow/Haul mode. Yea....a whopping 9mpg. Yeahaaaaaa. Man I miss my diesel.

 

If I am just driving down I-5 (straight, flat) going 70 with a trailer, do I really need to have the tow/haul? I would think that would be OK and get better mileage.