85 Camry LE stuck in 1st gear

I have an automatic 85 Camry LE with 102,000 miles. I began to notice last year that sometimes the car won't advance to the second and third gears. The situation is getting worse. Now, it won't shift to 2nd & 3rd gears 90% of the time. If I keep driving it, sometimes it goes into 2nd and 3rd gears but I don't know when or why. I am afraid to drive it because the fastest I could go in 1st gear is about 25 miles per hour at 3000 rpm. I don't want to push the rpm any higher afraid of damaging the engine.

Another thing I noticed is that when the car is stuck in the 1st gear, the shift indicator light is always in 'R'. When the car is shifting correctly, the indicator light shows 'D'.

I can't speak the the specific car but transmissions generally shift based on manifold vacuum (detects load) and throttle position.

Just and idea - check for a vacuum device on trans and if so make sure hose is ok. Look at the throttle area for anything broken. Good luck - may not be a whole trans job,