Just curious what the difference is.

 

O/D just locks out overdrive. Tow/Haul changes transmission shift points.

 

depends on the year too..

in 04.5 tow haul, only had a tow/haul switch and it extended the shift points and prevented OD.. I had one of these trucks and would use tow/haul up to about 55mph, then turn it off, so I could get into OD.

In 05, it is a tow/haul mode, but will go into OD..

In 06, you can turn on tow/haul, that will still enable OD, but if you push the button again, it will lock out OD..

Sorry don't have details for before 04.5 and after 06, but have driven these three years and the behavior is different

Bryan

 

The 03-04 is the same, OD off only with no shift enhancements. The 05 is the first year with a true TH that modifies shift pattern and lockup strategy.

The 06-07 trucks had both. The OD off was just a standard shift\lockup program while the TH had the more aggressive shift\lockup.

 

"lockup strategy"... I like it..

but yeah, in '05, the TC locks up in 2,3 and 4

 

In what gears on an 04.5 does the trans lock up? I know it does in 3rd (in T/H) and OD because I have felt it. Will it lockup in 2nd as well?

 

Not sure whether the 04.5 will lock in auto 2nd, my feeling is it won't but thats a guess. It might in manual 2nd.

My 05 locks in all 4 gears but it has been tweaked a bit.

 

I thought I read somewhere that it does lock up in 2nd. I only had one occasion towing where I had to use 2nd. I was going up a pretty steep climb on a mountain road with lots of switchbacks. It kept hunting between 2nd and 3rd, so I put it in 2nd and took it easy. I don't recall whether I could feel it lock up or not. Fortunately, it wasn't long climb.