Drive vs. overdrive

[cloverm]

I just bought an old truck with automatic transmission. By default it drives in overdrive, but it can be turned off with a switch. I have no clue what the difference is between drive and overdrive. When should I turn it off?

[trickster]

As far as I know, Overdrive will give you less power and a better gas mileage vs. overdrive off.

[Stix]

Think of a 5 speed manual transmission, Overdrive is simply the difference between 4th and 5th gear. In your case 3rd gear(Drive) and 4th gear(Overdrive). Overdrive's generally good for freeway driving.

[ASCI_Blue]

Overdrive (aka sportmode) also allows you to mash the accelerator without dumping a quarter tank of gas.

[cloverm]

Thanks guys, but I'm still not clear on when I should turn it off.

[creedon]

According to my son-in-law, automatic overdrive should never be used at speeds below 45-50 MPH; he runs a shop that specializes in automatic transmissions, so I think he knows what he's talkin about; he says that using O.D. at low speeds causes excessive slippage in the clutch packs, this leads to overheating, and heat is an automatic transmissions worst enemy.

[Ashcrow]

I've been confused about this as well. I looked in my manual for my car and it says I should always use overdrive unless I am going to be driving slowly.

[Tyr_7BE]

The general rule is that city driving = normal, highway driving = overdrive

And make sure you turn on overdrive on the highway. Otherwise you'll be going highway speeds in 3rd gear (distinguishable by the extremely loud, high-pitched hum the engine makes). My mom didn't do that once and sure enough the transmission overheated...cost mucho $$$ in repair bills upon arrival.

my transportation comes with overdrive as well... strangely I call it up and down hill.

[pwrhouse]

Only time you really need to turn it off is if you are towing something or hauling something heavy.
Other then that it usually only goes into overdrive when you are cruising at around 40-45 mph.

Congrats on the truck.