[markbrit]

This may sounds silly but I have no manual for my 2000 truck and I do not want to mess up my tranny.

When I want to turn overdrive off am I supposed to do it before or after I am in "drive"? Can I do it when I see a hill up ahead and anticipate it? What if I am currently in overdrive?

 

[Big Joe SS/T]

turn it off when you feel like...or never turn it on. its up to you.

 

[LoudRam]

Usually you'll turn it off when your towing on hills or while your in 4wd. If your in 4wd typically your not going fast enough to need o/d anyway. If your driving on steep hills (without towing) you might want to turn it off then too.

 

[mikeah169]

The shop that put my new gears in said to turn it off if i'm just driving around town, and once I get up to speed on the highway then turn it on.

 

[MuskratJames]

There's really only three times you'd ever turn it off:

1. When the tranny starts hunting gears, esp. when towing or hauling. Hunting those gears can quickly overheat and kill a tranny. If you're on the flats and it'll hold o/d, you can leave it on, but I usually just choose to leave it off anyway; you'll get more response and if towing maybe even better fuel economy since the engine's in its torqueband.
2. When off-roading.
3. As a downshift to glide to a light or to modulate your speed going downhill, or for passing without having to kick it down using the go-pedal.

Otherwise, o/d is better thought of as simply 4th gear. It's there for a reason, to save you gas when driving normally, and reduce wear while it's at it. Let the trans do its job; except for those instances up there, you're not going to do a better job than the tranny.

 

[Road Dog]

I turn O/D off when towing. When it's off the TC will lockup in third which might help around town when you're too slow for 4th anyway.