My 1991 300D 2.5 Turbo with 722 418 transmission will not shift out of first gear. I've owned the car over a year and except for shifting a little hard when cold the transmissions been OK until one day when it just stopped shifting. I've disconnected the downshift switch beneath the accelerator and made sure the Bowden cable was adjusted with the slack taken up but not pulling. I'm not sure where to go from here. My first for everything. MB, diesel, posting.