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I have read the owners manual and tried to follow post on this web site but still not completely clear on when to use T/H.. I have a 5er 10k 30ft. Am I incorrect in pullin in T/h until I am up to speed on the hwy then,if am traveling on a mostly flat road (ie ohio,indiana ill ect) I set the trans back to regular hit cruise and enjoy the ride?? or am I suppose to leave T/H all the time I am pulling?? I Have not pulled since adding juice and have every intention to set T/H lvl1 regular trans lvl2. does this sound prudent to presereve allison?? Thanks in advance..
 

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I would suggest T/H whenever towing. It will change your shift points and you might find it hard to hit 5th at cruising speed until you get going pretty fast. It sure is a handy feature, and I sometimes use mine even running empty if in the hills to help with slowing and downshifts.


I can't comment with authority on juice settings, but I'm sure somebody will chime in and tell you what is OK.


Jim
 

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David, I'm not towing quite as much as you, (6K lbs) but my juice setting are as you suggested, level 2 regular, level 1 T/H. I generally only use T/H only when in the city or expecting braking. I do not use it on highway, as it never hunts or downshifts, ever. I have never used it empty in the mountains, as the grade braking function on mine works wether in T/H or regular mode. If I am coming down a steep hill on the brakes, grade breaking kicks in pretty quickly, and it will begin downshifting. Go figure.
 

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I use the tow/haul mode whenever I am towing. It changes the shift points and also does an extremely effective job at grade braking.


Additionally it locks the converter in all gears. Your transmission runs much cooler.


There are different modes.


Press once = No Overdrive


Press twice = No Overdive + Haul mode


Press three times = Overdive + Haul mode


Press again = normal with Overdrive


I noticed that after I cycled through the settings all I have to do is press once for it to toggle between normal and Overdrive + Haul mode.Edited by: JohnnyO
 

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is it the same with '02's. I hauled my Dad's 5er from las wages to wi going the southern route (Az,NM,Ok,Mo,Il) and never really noticed anything with the t/h on or off. my milage was definatly different 19+ going to LV vs 14 on the way back. speed out was avg 90, coming home avg 80. Should I have noticed anything or did I not have it set right? Input and comments welcome. thanx, AkDually61
 

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Hmmm Didn't know there were different modes, thought it was either on or off T/H mode, learned something new today!
 

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JohnnyO said:
I use the tow/haul mode whenever I am towing. It changes the shift points and also does an extremely effective job at grade braking.


Additionally it locks the converter in all gears. Your transmission runs much cooler.


There are different modes.


Press once = No Overdrive


Press twice = No Overdive + Haul mode


Press three times = Overdive + Haul mode


Press again = normal with Overdrive


I noticed that after I cycled through the settings all I have to do is press once for it to toggle between normal and Overdrive + Haul mode.

Actually that is not right. The way it works is when you tap it (press quickly) it shuts the tow/haul mode on or off. When you hold it down turns the OD lockout on or off.
 

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So what really is the difference between the T/H and the overdrive lockout? I can't tell any difference with normal driving, but I havent had the opportunity to try it while towing.





RussEdited by: Duramaxdad
 

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Here's my take. On the 03 if you hit the tow haul button for 1 second or quickly you will engage towhaul. If you hit the button for 5 seconds you will lock out overdrive. You can use towhaul with or with out the overdrive lockout funtion. You can use OD lockout with or wiht out T-haul.


Gm reccomends tow haul anytime you are towing 75% of the total load rating or more. Tow haul does change the shift points and locks up the converter. It also lowers the point at which grade breaking begins. Meaning that normal downshifting would almost be unoticable, however with towhaul engaged it really becomes apparent that your truck is down shifting and staying in lower gears when using the breaks.


As far as the Overdrive lock out is concerned. This is my take. Under normal conditions your vehicle from a stand still will upshift through all 5 gears. 1,2,3,4,OD. Down shifting your transmission may or may not go OD,4,3,2,1,. If you pull the gear select lever down from D to 3 you miss 4rth. So you never get to use 4rth. gear. That is why it is so obtrusive to shift from D to 3 at highway speeds. You are actually downshifting 2 gears.


Real life tranlation. If you are towing with the gear selector in D and your engine is searching for gears your best option is to hold the T-haul button for 5 seconds and lock out overdrive. You will then be using 4rth, gear as your highest gear.


It is also a good idea to use this same logic coming down steep grades. Just lock out your OD and you will avoid a runaway condition. If you use OD lock out in combination with towhaul and your 4 wheel anti lock, huge 13" disc brakes, I think you find this as the next best thing to an exaust brake.Edited by: Bronco
 

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[/QUOTE] Actually that is not right. The way it works is when you tap it (press quickly) it shuts the tow/haul mode on or off. When you hold it down turns the OD lockout on or off.[/QUOTE]


Hi Max Power:


I havn't tried your method yet. What I am going by is the indicator lights on the dash board.


When I am in normal mode and tap once, the light comes on that indicates no overdive.


I tap again, the no overdrive light stays on and the haul light also comes on.


I tap again the no overdive light goes out and the haul light stays on.


Next time I am in the truck, I am going to try your way and see what happens. Like someone said You learn some thing every day here.


Thanks!
 

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ok... nobody has answered my question yet? is this the same on the '02's? thanx,
 

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AkDually61 said:
ok... nobody has answered my question yet? is this the same on the '02's? thanx,

Sorry. I am not ignoring you, I just don't know about the '02s.
 

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It's the same to activate tow/haul on the 02, but you can't lock out overdrive. That option started in 03. Hope that answers it akdually61
 

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AkDually61 said:
is it the same with '02's. I hauled my Dad's 5er from las wages to wi going the southern route (Az,NM,Ok,Mo,Il) and never really noticed anything with the t/h on or off. my milage was definatly different 19+ going to LV vs 14 on the way back. speed out was avg 90, coming home avg 80. Should I have noticed anything or did I not have it set right? Input and comments welcome. thanx, AkDually61
AkDually61,

As previously indicated the '02s don't have the OD lockout as standard option but a GM approved install is available for both '01s & '02s.

Your best bet is to contact Eric Merchant (DmaxAlliTech) on this forum as a vendor as to cost of the kit and how much it should cost to install or have it installed.

My 5th whl is about your size and after pulling just once I can say it helped a lot. I run in the Sierra Nevada Range quite a bit and feel it is a real advantage to be able to manually select when I want to run in 4th gear - uphill or downhill - plus I can manually make the change from 4th down into 3rd rather than have the Allison drop into 3rd from 5th
Hope this helps a bit.

Bill
 

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All I know is that my Duramax take off harder than eny other I have had them all powerchoke,cummins,and my new Dmax it is the onlgy one with towhaul and i have suped them all up and my Dmax would still take them stock the towhaul help on take off and it helps a bunch on hauling
 

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Max Power said:
The way it works is when you tap it (press quickly) it shuts the tow/haul mode on or off. When you hold it down turns the OD lockout on or off.

That's the way my '04 works. I'm glad I spotted this thread and the input on it. My salesman had not shown me how that worked and for some reason, I'd not looked it up yet in the owner's manual.


It does explain why the switch has a long arrow with the OD lockout symbol, and a short arrow with the trailer symbol. Now I understand....
 

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My 03 Gmc works the same as Maxpower described and so does a buddy's chevy. Try yours again JohnnyO- I would think it should be the same.
 
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