Where is the overdrive switch located on a 1999 Ford Taurus it and when switches gears feels like motor going to fall off.?

The overdrive button (or switch) on a 1999 Ford Taurus is typically located on the shift lever itself. It's often a small button, sometimes illuminated, that you push to engage or disengage overdrive. Look closely at the shifter; it might be on the top or the side. Your owner's manual should show a picture and explain its operation.

Regarding the feeling of the motor almost falling off when shifting, this is *not* normal. This sounds like a serious problem, potentially related to:

* Transmission issues: Worn-out transmission components, low transmission fluid, or internal transmission damage could cause harsh shifts and the sensation you describe. This is a significant concern.

* Engine mounts: Worn engine mounts can allow excessive engine movement, leading to vibrations felt during shifting.

* Driveshaft or axle problems: Problems in these components could also cause vibrations and harsh shifts.

Do not continue driving the car in this condition. This sounds like a potentially dangerous and costly repair. You should have a qualified mechanic inspect your Taurus immediately to diagnose and repair the problem before further damage occurs. Ignoring this could lead to more extensive and expensive repairs, or even a breakdown on the road.