When pulling heavy load (18k) I put it in tow/haul but it seems to still have all gears, I thought it would stay out of overdrive. Is it pulling in overdrive?

Mine does as long as the button was pushed before I started. If I hit the button mid cruise it downshifts and stays a gear lower. I have found it pulls much better in tow/haul when I am towing.

2005 has two options, I believe they are tow/haul or OD off.. but not both like 06+

I have not found od off, just tow/haul.

With a DRB the dealer can make it OD off, but you don't get to go back and forth if I recall correctly. I don't know if there are mystery switches you can install to give OD lockout??

tow haul on a 05 holds gears longer before up shifting and downshifts sooner while braking.....that's pretty much it.

Ok, thanks everybody