Automatic Transmission - No Overdrive
 

My wife recently bought a 1992 Mustang LX 4cyl 2.3L
when she bought it, when the car was in drive, after hitting ~55 MPH, she would have to manually switch it into overdrive
starting today, when she switches into overdrive, the car starts revving high and losing speed. when she switches back to drive, it just revs high until she was stops.

i'm sure this can't be a good thing, but give me any good news you can!
also, i apologize if this is posted in the wrong section :(

Dumb question but have you checked the tranny fluid?

definitely not a dumb question because i was hunting for the dipstick today.... however, i'm dumbfounded... where in the world is it? i can see everything but the transmission fluid dipstick and refill...
(forgive me, we've only owned this car a couple weeks!)

well according to the manual from my '91 the trans dipstick (when looking at the engine from the front of the car) is on the left side at the back of the engine, right at the corner of the cam cover.