My 77 300d will not shift unless I drive to redline, then let off the gas. I fixed a leaky tee, which solved the engine run-on, but still have this shifting problem. Where do I start? Vacuum to the tranny? I've read many threads leading me to assume a faulty modulator, but also have been told about a bowden cable? The shift from 2 to 3 is much easier, not requiring me to redline nearly as much, yet I still must let off the gas pedal to get it to change gears. This is a w123 chassis, 195k miles. Any help is much appreciated.
Craig N