Ford Repair: overdrive, overdrive band, ford taurus

Question
I just bought a 93 ford taurus gl, with overdrive. the owner told me to shift it into overdrive when getting up to 45 mph. He told me if I just drive in overdrive I will ruin the transmission. Isn't it bad to keep shifting it back and forth? I travel on a highway 45mph, but their are stoplights, so when do I downshift? Should I just drive in drive if i'm only going 45 mph? And what happens if I don't shift it correctly?

Answer
Brenda-

  Well...you fall into the in-between category of whether to use overdrive all the time or not.  Normally you don't want to use overdrive unless you're at highway speeds.  The reason is that the overdrive band is the weakest link in just about any automatic transmission and constant automatic shifting back and forth (when putting it in overdrive and driving around the street) can wear it out a lot sooner than the rest of the transmission.  So yes, usually it's best to manually shift the transmission once you reach highway speeds.  At 45mph, I would just leave the transmission in 3rd gear anyway.  I tend not to shift into overdrive until I hit about 55-60mph.  But it's all in how you drive.  Just remember the idea is to keep the transmission from shifting up and down from overdrive to third (or vice versa) all the time.  Hope this helps.

Steve