I have an '04 duramax quad cab, when I use the Haul button will the trans lock up in overdrive once I'm up to speed and cruising ?

Thanks in advance

It will lock the torque converter as for locking in overdrive it wont. It will down shift sooner to reduce the chance of lugging the ehgine to much. Hope this helps Kyle

It won't "lock" in overdrive, but it will still go into overdrive. If you HOLD in the tow/haul button for a sec or 2 then the Overdrive lockout light will come on and you are locked OUT of overdrive. With just tow/haul, you still get overdrive, but different shift patterns and grade braking. At least this is how it is on my 05.

Thanks guys

In tow/haul the convertor is locked up in second gear and up, also changes shift rpm's and raises the pressure a bit for firmer shifts

:exactly:
:welcome: to the diesel place. The torque converter always locks in overdrive (above about 50 mph.) Tow/Haul mode will lock the TC in second gear and up. It also downshifts while you brake for more stopping power.

One last thing....... A duramax into a QUAD cab is a Helluva conversion. Only D*dge makes quad cabs. GM builds Crew cabs (four full size doors and a real back seat) and extended cabs (suicide doors and seating for kids or short trips.)

DUW,

Welcome to the site. The link below will give you some info on how the Allison works in these trucks:

http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3931EN.pdf

my 01 will shift to 5th at 60mps in tow haul mode empty or loaded. and lock in 5th. but it does d/s easy if u hit a hill. the best part of tow haul is the engine breaking power the harder u hit the brakes the more it downshifts. i love it!!

Welcome to the site, and a quad cab is a dodge!!!! Just Kidding!
I hope you like your truck, these guys have ya set up on the tow/haul thing.