When to use overdrive?

Sorry for another newb question, but I never did learn this - at what point do you use overdrive? I don't have the push button OD like some birds, it is a seperate position on the gear shifter. I just realized that I have been driving around everywhere in overdrive, and didn't consider the consequences of it. Are there any consequences? If so, what are they?

My Bird is a '93 3.8L automatic, btw.

Thanks in advance.

It is actually best (easiest on the tranny) not to use OD unless you are going to be driving sustained speeds of 50 or faster.

Cool. Thanks a lot, man.

I do not know if you have decided what to do yet about the OD, but I am a former officer with Cleve and Broward and we noticed by leaving the OD on all the time, it helped make all the related components, and the trannies, last longer. You save a ton more in gas leaving it on, the engine is practically idling in OD gear. Also, I have experienced other drivers telling me that the switching often from on and off can cause electrical and function MALfunction over time. I leave mine on ALWAYS in all my 4.6's, t-bird, interceptor, and marquis...so now you have two opinions! Good luck!!

Mike75, Birdlover is 100% correct. If you keep switching between OD, and D, you will eventually screw up the tranny-I personally know this. About 2 months ago, i got my first t-bird, it's a 95 4.6, and i left it with the OD off, cause you'll notice the car is faster from like 0-40 speeds, cause it stays in first gear longer. Well, over the coarse of doing this, i sometimes forgot to switch OD off, and therefore switched between OD, D, etc. Now i'm experiancing shuddering like mad, especially if i drive at cruising speeds, then give it gas slowly, man, feels like driving over metal strips. Yesterday i got the entire tranny flushed, even the torque converter, avis put in new filter, and mercon V, still the same problems.

I'm just gonna drive it till it explodes :-)

You don't need to turn overdrive off unless it is shifting back and forth between drive and overdrive this will burn overdrive up. This ussually only happens when something is being pulled so you probably don't need to do this at all.

Cool thanks everyone. I have only been driving in OD anyways, since my car seems to run much more smoothly this way. Great to hear it is okay to do. Thanks again!

Mike75, Birdlover is 100% correct. If you keep switching between OD, and D, you will eventually screw up the tranny-I personally know this. About 2 months ago, i got my first t-bird, it's a 95 4.6, and i left it with the OD off, cause you'll notice the car is faster from like 0-40 speeds, cause it stays in first gear longer. Well, over the coarse of doing this, i sometimes forgot to switch OD off, and therefore switched between OD, D, etc. Now i'm experiancing shuddering like mad, especially if i drive at cruising speeds, then give it gas slowly, man, feels like driving over metal strips. Yesterday i got the entire tranny flushed, even the torque converter, avis put in new filter, and mercon V, still the same problems.

I'm just gonna drive it till it explodes :-)

I want what he's smokin.

I know this is old, but im new here, sorry... when I put my car in overdrive the RPMs are higher... this is contrary to anything ive ever heard.. I havent tested this out much at highway speeds though... is that why?... and If I was cruisin thru the city, and then hopped on the highways, would it hurt to switch O/D on and off in that case, or is that what you all mean by switching it too much?

RPM's higher? i have that problem idling in park or neutral but the RPM'S are regular a little bit under 1,000 like im thinkin there supposed to be through drive and overdrive.

Ok I have a 95 "T" 4.6 yes I had the trany flushed with tc also....but with a old mechanics request I added Dr Tranny. 6 ounces of feel good stuff... comes in a smal red tube and it does wonders for all that "feels like going over metal strips" stuff.... stops it in its tracks....... just a thought for you all... keep on truckin