Hi guys, I'm new here. I'm not too mechanically inclined so I've come here in hopes that y'all can help steer me in the right direction.

I have a 1999 Ranger 4 cylinder (2.0L or 2.3L?) with 170,000 miles on it.
The past week I've noticed that my transmission has been shifting poorly in lower gears. Also it seemed to stick in third gear for longer than needed.

Yesterday while accelerating on the highway, my transmission slipped out of gear and freely revved, refusing to get back into gear.
Luckily I was able to coast off the highway into an exit.
Eventually the O/D Off light came on (not blinking), and the transmission shifted back into gear.
When I reached a stop, I tried turning the car off and back on. The O/D Off light turned off, but the car refused to shift into gear when I put it in 'D'.
Eventually the transmission caught when I shifted it into 1. The O/D Off light eventually came back on.


Now, the only way I can get the car to drive is to put it into 1, let it idle for a second till it catches (I can feel the car jerk when it gets into gear). Then, while driving, shift to 2 until I reach a high enough speed to shift into D.
It seems like I have to reach third gear for my D to work, but now third gear sticks longer and runs up to much higher RPMs. It almost sounds like I'm red lining the engine till it finally switches to 4th.
4th and 5th gear seem to drive fine, but if I slow down too much while in D the truck will slip out of gear and I'm basically coasting in neutral.
Also, now when I shift from 1,2, and D to reach speed, I notice my O/D Off light doesn't come on.

After class today I'll do some tests to see if I can get the O/D Off light to come back on.


Any ideas what the problem could be? Are there any tests I can do myself before I take the truck into the shop?
I've done some reading, but since I'm not too knowledgeable about these engines/trans I can't help but wonder if I'm looking at the wrong information.