I would like to change the way the overdrive tow/haul switch works so that you tap to turn off th O/D and press and hold for tow/haul, if that is possible.

Thanx Tom C.

Why?

Not possible, sorry. It would require reprogramming of the BCM and I haven't seen anyone able to do custom BCM tunes to date.

Why?
I don't tow very often (about 6 times a year) but I do like to lock out the O/D frequently like when it's cold and driving in town and occasionally for downshifting.

Thank you for the reply Max Power, I figured it would be something like that.

tom c

Personally, in those situations I would not lock out OD. (in town)

Personally, in those situations I would not lock out OD. (in town)I've heard all sorts of things on this subject and the diesel mechanic a work told me I should'nt use the O/D in town, that it causes excesive wear on the tranny.

edit: Is the O/D lock out in town just an old wives tale, urban myth???

Well I guess it could be an issue of the transmission was hunting back and forth between 4th and 5th. The allison is a very heavy duty transmission and you don't need to worry about it making a few shifts in and out of OD. I wouldn't concern myself with it at all.

Thanx again Max, U da Man!!!

You must have fast speed limits in your town if it can get into 5th. It shouldn't be in 5th until 45 or so...

You must have fast speed limits in your town if it can get into 5th. It shouldn't be in 5th until 45 or so...

No, it's just that everyone drives 45 mph in the 35 mph zones. Mine seems to shift into 5th around 42 mph.

I think what you feeling is the TC locking up. I've never had mine shift until about 53 mph and I baby mine. If I remember, 42 is about where 4th is engaged.