Why does car shift funny and go into limp mode?

89 Chrysler New Yorker, 3.0, A604 , fwd, I bought a car it shifting perfectly first day. The next day the starts to go in and out of gear (3rd gear) around 31 MPH and even neutraling out sometimes, not really slipping just going hard in gear then back out. On board computer reads "check trans" right after car goes in limp mode. Replaced input and output speed sensors and engine temperature sensor but it didn't help. Not sure if it's related but ABS light came on a day or so later and the breaks got spongy and low coolant light has been on since day one and coolant is not low.. Car goes in limp mode everytime I drive it, forcing me to drive around in 2nd gear, any suggestions?