I have a 1987 240 Wagon with automatic transmission. Just the other day it rolled over to 261,000 miles. However, a few miles after that, I was driving about 60mph and the shift indicator light came on and the car downshifted. I had to drive 50mph or lower after that in order to not feel like I was pushing the engine too hard. It still shifts through 3 gears, but seems like it should be shifting into another gear. The shift indicator light comes on when I start the car, and stays on. When I push the downshift button on the shift knob, the light gets slightly brighter, but it does not downshift like before. It seems like this could be a quick fix, but my Haynes manual gives me no help. Any suggestions?