I just purchased a 1984 C10 pickup truck. I noticed it has P R N OD D 2 1 on the gear shift. I wanted to know when I should use the OD vs. the D

 

Depends on what you're doing...

There's probably only a slight difference in the ratio between D and OD. Some transmissions are smart enough to be able to select OD and give you better mileage...that being the key to using it.

When driving in town, you could select D for a ways (1/2 tank), check your mileage, then try it in OD and see if it improves. I would suggest that you use the OD when on Hiway.

When towing, often times on hilly terrain, using D is the preferred, because of too frequent downshifting.

It won't hurt to use either, so, just play around with it, and see how it fits your driving stile...and pocketbook :biggrin:

 

Thank you for that information, it was very helpful. I will definitely use D when towing anything

 

Don't lock anything down as absolute !
There may be conditions (flat terrain) where using OD when Towing is quite appropriate. Be flexible and alert.