I have been reading aobut adding an overdrive lockout switch for the Allison. Then I read onthis forum that you can hold the tow mode switch in for 5 seconds and over drive will lockout. I tried that last night and here is my sequence:


started truck


pushed tow mode (light comes on)


pushed and help for 1 second (Overdirve locked out - light came on)


pushed again for 1 second (over dirve lockout off)





The question -- did GM add the lockout on 04's and my sales guy did not know it? (not surprised) I was all ready to add the switch and then found this procedure. Anyway, not complaining that I don't have to add a switch just confused (which my wife says is normal for me).


Don (gearing up for the 2500 mile spring break fifth wheel hauling vacation to MickeyLand) Miller

Yes, GM added this feature in 04.


Your owners manual will tell you all about it too. http://www.dieselplace.com/forum/smileys/Big Smile.gif


Push the button once breifly it will go to tow/haul mode.


Push and hold the button for about 3 seconds it will go into O/D lockout.


Push it in breily again it will go out of tow/haul mode.


Push and hold it again for 3 seconds it will go out of O/D lockout.

well i also have it on my 03

REad the Owners Manual....That's just not Natural!!!





Don (Sometimes I long for the old days of push button transmissions) Miller

I know...I know


I don't either until the last straw, but when you do, sometimes you can find interesting stuff!

it became standard on the 03's