Overdrive

[tstammer]

I have a 2006 2925RK BigHorn and tow with a 2006 GMC Dually Diesel I do use the tow haul mode, was wondering when If anyone switches to overdrive when up to speed. (60-65 MPH) just curious.

I have a 2006 Gmc 3500 Dually Diesel I use the tow mode I was wondering if anyone switches back to overdrive when they are up to cruising speed?

 

[jpmorgan37]

With my GMC, I used overdrive most of the time and kept it in the tow haul mode, especially when I was on Interstates or even good two lane roads. When I got into the coal mining area on some of the twisty turney up and down roads, I would drop out of OD. I do the same with my Ford PSD.

John

 

[cdbMidland]

My 06 Dodge 3500 has a Tow/Haul mode and overdrive. My RPMs in Tow mode are the same that I have in OD when I am not hauling at highway cruising speed, so I have to believe that I am in OD with the Tow/Haul mode engaged.

 

[sislv]

I use overdrive all the time when we're traveling in fairly flat country and switch it off when coming to steep hills. I try to keep the rig from bogging down mainly.

I usually travel in the rightmost lane @ about 60 mph on Interstates and let most traffic pass by. Nice and relaxing driving.

Tom

 

[mufflerman]

In 2006 GM duramax/allison trans. is a 6 speed with drive & manual range, It also has the tow/haul mode.
What overdrive are you talking about?
Is there a button or switch that I don't know about?

 

[nhunter]

I leave mine PSD in drive with tow/haul mode on and leave it alone.

 

[Goldenwingers]

Ray, on my 2005 Allison the button at the end of the shift handle is both for tow haul and overdrive lockout. Press and release for tow haul and press and hold for more than one second then release for overdrive lockout.
Don

 

[Chulinw]

I always use the tow haul mode when pulling w/Allison. I let the engine and Allison work together to slow down when exit the highway.

 

[mufflerman]

Don, - goldenwingers,
I had an 05' with the 5 spd allison and I don't believe the tow haul mode locks out 5th gear, I now have an 06' with the 6 spd allison and manual mode, it also has the tow haul mode and when I use tow haul it does not lock out any gear it just down shifts sooner for more engine braking.

 

[Forrest Fetherolf]

mufflerman,

You are correct with the six speed allison tow/haul mode, the torque converter locks up and 6th is still there. The only way to block 6th is with the manual shift rocker switch. I have noticed that mine stays in 5th longer than I prefer, so I switch tow/haul off, let it shift, and then turn back on.

Forrest

 

[5catfam]

I have a 2006 GMC and I have observed that when you are up to speed the RPM's are the same, no matter if you are in the tow haul mode or the normal mode. I am talking about Highway speeds on level ground. This tells me that I am up in the 6th gear.

 

[jwb187]

On my 05 GMC equipped with the Allison, when towing I have the gear selector switch in the "D" position and also have tow/haul engaged. This seems to lower the shift points and also engages the auto braking feature. When in hilly terrain and the engine starts bogging down, I hold in on the end of my shift selector for a second or two and this drops the transmission down into the next lower gear which I call shifting out of overdrive. I never have to adjust the gear selection lever manually into 3,2,1. This has worked for me.

 

[Goldenwingers]

jwb, I was beginning to wonder if anyone knew about the overdrivre lockout but me.

Don

 

[jwb187]

Hey Don,

I still kind of get the impression that some don't know what we're talking about with the tow/haul button. It took me a few months after I got my truck and was on a trip out west and talking to another rv'er with a duramax before I found out about the down shift switch. He said to me "boy that down shift switch sure makes it easy on some of these grades doesn't it".....I said what switch is that.....he then showed me what he was talking about......I felt sort of stupid for a while as I had manually been down shifting into third up till that time....JWB

 

[Simmons]

I always have it in the tow/haul mode when towing and the rpm's between 2000-3000.

 

[Goldenwingers]

I leave mine in drive with tow haul engauged and only take it out of overdrive when in the mountains in a hard pull.

Don

 

[bill40]

Don, I do the same (seeing we have twins)has always worked well. We hit a 7% grade for 14 miles on RT 40 west last year. was dreading the downhill side but everything worked well.
Bill

 

[MurrayN.]

I also have to admit that I found my overdrive lockout by accident on day. It sure made life a lot easier when you can stick it in drive and leave it there when you want too. How many of you guys have exhaust brakes put on your diesel? There is nothing that has made my Duramax more of a pleasure to drive than having that exhaust brake purring away as you coast down a long grade and slow down without touching your truck brakes. It was worth every penny as far as I am concerned.

 

[wyleyrabbit]

So let's see if I understand...if I want to drop out of overdrive, I press and hold the tow/haul button for 1 second?

What is the benefit of doing this? Wouldn't I be better to put it in tow/haul mode, and set the cruise control for a comfortable speed, and let the computer and Allison do the work of keeping my speed down?

 

[bill40]

I also have to admit that I found my overdrive lockout by accident on day. It sure made life a lot easier when you can stick it in drive and leave it there when you want too. How many of you guys have exhaust brakes put on your diesel? There is nothing that has made my Duramax more of a pleasure to drive than having that exhaust brake purring away as you coast down a long grade and slow down without touching your truck brakes. It was worth every penny as far as I am concerned.

Hi Murray,
Was going to put the new Banks brake on till I called and got the price. I'll probably wait until we take our next trip out to the north western states. Think I will need it in those areas.
Bill