New to forum and looking for help.
I have a 1988 560sel with 107,000 miles. the transmision is stuck in second gear. last weekend I changed trans fluid, filter, and modulator valve. This solved the problem 2 years and 10,000 miles ago, but not this time. Any advice as to where to look for problem next. Or how to fix welcome.
BC

 

The trans modulator valve only effects how firm or soft the shift is.
You could check the kickdown switch to see if that is faulty, but that would only
be for the drop/shift down from D to 3. Passing gear.