I just purchased a 1990 Mercedes 300SEL with 84,000 original miles. The car is in excellent shape, but the service history is unknown. I have only put about 1500 miles on the car so far and have been trying to catch up on all the maintenance items. The transmission has operated flawlessly for me until today. I was driving on the express way and took a clover leaf on ramp at a pretty good rate of speed, and suddenly I felt the transmission downshift into third. It wouldn’t up-shift back to fourth so I pulled off the express way and limped it toward home in second and third gear on the back roads. Suddenly after about 15 miles of back road driving the transmission up-shifted into fourth and now seems to be functioning properly in all gears again. The fluid level is perfect, but does look like it needs to be changed (and it was on my list). The fluid does not smell burnt or strange like there was any kind of additive in it. Any idea what could be going on?
Thanks for any and all ideas.