Ford Repair: 1992 Taurus 3.0L with AXOD-E tranny, cv axle, taurus 3

Question
I have a 1992 Taurus with the 3.0L engine and the infamous AXOD-E tranny with overdrive. This same condition occurred a few months ago, but I will only tell you about this most recent occurrence. While on my way home from an amusement park in PA with my fiance and 2 kids, the automatic tranny popped out of 4th gear. I slowed down a bit ( I was going roughly 70 ) and it dropped down to 3rd. Unfortunately, it would not go back into 4th. I also noticed a whining noise coming from the engine, but I could not tell if it was the tranny or the engine as the engine was at higher rpm than normal. I pulled over and checked for any signs of external damage to the tranny, and there was none. I pulled away and the car shifted through 1st, 2nd and 3rd smoothly. It still would not go into 4th. I pulled over again and checked the fluid level 3x and it read full. I added half a quart of tranny fluid and continued on my way. Luckily, I had gotten hold of another family member that was only a few miles ahead and they followed me for a good 50 miles. The tranny shifted smooth as glass through all gears. I was given this car about a year ago after the Saturn that I had went to crap. The car was purchased by my uncle at an auction in PA, so I know little about the history of the vehicle. I do know that all recall items were repaired/replaced. I have been diligent with the routine maintenance as I do not know the history of the vehicle. I personally have flushed the radiator, changed the oil several times, flushed the brake system, changed a front CV axle because it showed a little sign of wear ( torn CV boot ), flushed the power steering system, and done a full tune-up. The only thing that I didn't get to was the transmission. I have been told by a few gearheads that when it comes to the transmission, if it's not broke, don't fix it. I know a little bit about transmissions, but not much. I have several ideas about what it could be, but I can't say definitely one way or another what the problem is. Is it possible that the dipstick is the wrong length and therefore would read full when it actually isn't? I would like to know what length it should be so I could compare it to what is in there now. Is it possible that one of the ports in the valve body plate ( I believe that's what it's called... the plate with the holes in it that directs the flow of the ATF ) is partially clogged and needs that extra pressure in the tranny to shift into 4th? I know that it's not good for the tranny to run at a higher pressure than the specs call for or you could blow the gasket or much worse. I am at a loss when it comes to transmissions on front wheel drive cars...... PLEASE HELP!

Answer
Hello and thanks for the question...I'll try to help.
Your gearhead friends are right.if it ain't broke......don't fix it. BUT...yours is! What I would suggest is a few things:
1. Transmissions service ----IF there is a lot of debris in the pan ..put it back together and bring it to a transmission shop.
2. Check the 3-4 shift servo.....If you look at the back side of the transmission you'll see two cover sticking out of it. remove the upper one. Check to see IF the seals are ripped or broken.

It isn't likely that your transmission has the wrong dip stick in it.
Erik