My '91 f150 2wd auto is pretty new to me and i was wondering when my electronic overdrive should be used?

 

All the time, just turn it off when the tranny is searching for a gear.

 

Check your manual if you have one. My manual for my 1988 F150 XLT, 302, AOD, 2 wheel drive, says the overdrive is the normal gear for all city/highway driving, and to only use drive gear or the lowest gear in other than normal conditions--ie. towing, hills, etc.--when the overdrive is switching in and out, like the above post said. Use of overdrive sure helps with the gas bill.
Frank.

 

That's what Ford tells you so it gets CAFE tested in O/D instead of Drive. In reality, your trans will work better, run cooler, and last longer if you pull it out of Overdrive whenever you are not driving at sustained speeds above 40 MPH. Below 40 (depending on gear ratio, this speed is approximate, not absolute) Overdrive is of no real benefit. A friend of mine is a Police Officer in my town and he said that Ford reccomends that they use Drive for patroling the streets, and O/D for Highway or Pursuit driving. And they are not the only ones, as Cheverolet used to give the same reccomendation for the Caprice cruisers. I would reccomend the same for your truck. I've got an AOD with over 120,000 miles on it, and with just regular fluid changes it performs as strong today as when it was new. I don't baby it either. I frequently tow a 6,500 lb trailer, and often haul up to a ton in the bed. I also commute with it every day (except fridays in the summer, when I drive my Hot Rod).

 

Ok but mine has the button for overdrive, is that the E4OD, and if its on will it give me better gas milage when im going 40 on my commute cause now im having to fill up my rear tank every other day ( i only use my rear tank cause the middle is busted).

 

if you are only cruising at 40 then it will constantly shift back and forth. keep the OD off.

 

I totally agree with ARGO, OD is for HW( hi-way) it is meant to go there and stay there for a while not jump in and out, under 45... stay outta ova-drive!

 

WARNING!! You might be pumping gas into the front tank! My truck does that. I fill up and run the front tank to a quarter, then switch to the rear. When the rear is dry, I switch back to the front and voila! The front is at three quarters full. Are you getting really bad milage (like 7-8 mpg)? If so, the fuel may not be returning to the rear tank, but instead going to the front tank. This can cause a spillover.

 

For those of you recommending not using overdrive except on the highway, can you please clarify a bit more for me: my manual for the AOD transmission indicates that the overdrive is the normal driving gear for both city/highway, with the drive gear being for towing, hills, etc. (I do not have a separate button to engage the overdrive, like I think the E4OD does).

When I drive from a standstill, I can see my tachometer going up to about 2,000 rpms where it shifts to the next gear, goes up again to 2,000 and shifts again, with the last gear being overdrive, and then it stays in overdrive on a city road at speed of about 35 - 40 mph (60 km/hr.). It does not shift in and out of overdrive at that point, unless I slow down for traffic, when it will downshift, before resuming normal overdrive speed. So I am really using the overdrive as an extra gear, and in overdrive the tachometre is at about 1400 rpms rather than about 2,000 rpms where it would be in the "drive" gear, so I'm also saving substantially on gas and maybe on engine wear. To me this still makes sense--am I missing something? Is this damaging the transmission?

 

No, you're doing it correctly. Leave it in OD unless it is frequently shifting in and out of overdrive.