I pulled my gooseneck trailer loaded ( 300 miles trip) and pushed the tow/haul button to kick it down and it works when going up a hill or grade but just as soon as you level off, it shifts into overdrive. It does this all the time. I keep having it push the button when it pulls hard. What's wrong? What do I need to check ???

 

The 05 doesn't have the OD off, I never pulled anything heavy enought to make it work hard on a hill without it shifting out of OD on it's own.

 

On the 07's there is tow/haul mode AND O/D off mode. In tow/haul mode the tranny will still shift into OD. Maybe there was a programing change in 05?
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My 06 has it the TH/OD off as well must have changed it along with the headlights...

 

All Tow/Haul (a.k.a. T/H mode) does is change the shift point in the transmission and once it gets up to a speed above 50 MPH and you let your foot off the go pedal it will shift in to OD. This is how T/H works and pushing the T/H button again just takes it out of T/H until you push it again. So as I sated above once its in T/H your transmission will shift back in to OD, once your speed is above 50 MPH and you let your foot up off the go pedal on flat road or after you top a hill and start back down the other side.

Your transmission knows when it needs to shift or not shift so let it do its job as if you keep hitting the T/H mode button sooner or later you going to screw up something in or to do with your transmission. BTW, it’s almost impossible for your auto transmission to lug your Cummins engine.

 

the 05 truck with the th engaged will still give you overdrive and until you meet a certain threshold the truck will not shift down into drive until it feels like it is truely necessary. what kind of a load you pulling or how big is it are you truely using this CTD or just toying with it?

 

I believe it was 05's that has the bastard program that will not lock out OD. every other year you can actualy lock out overdrive by hitting the button twice to turn off overdrive.

 

I know it will scare you coming down hill, I was empty but hit the tow mode in the mountains, coming down the other side with the cruise control on and it got over speed set, I figured it would just drop out, I felt the OD kick out and then it hit second gear to slow the truck down.

Going from 1700 rpm to 2800 will wake you up quick, so I hit the brake to cancel everything and went back to normal coming down the hill, just let it go and hang on.

 

I had a 30 grain drill (8000 lbs) on my 29' gooseneck trailer. It definitely didn't "toy" with it. I was in some hilly roads in west central MO after I got off I70. I've been around a lot of automatics and overhauled some and know all the shifting back and forth isn't good so I didn't know if the tow/haul button should have locked out OD or not....sure would havebeeen a good idea. I would ease up on the throttle when it would shift down so not to slip anymore than possible. I made the trip home but don't think much of the way that works.