Pulled the driver's seat out of my 1985 300CD because of a broken seat spring. The spring was easy enough to repair, however the seat track is proving problematic. First, the height adjustment handle on the side of the seat takes quite a bit of force to actuate and there does not appear to be any way to adjust the spring tension. Second, the seat track operation is very stiff because of a lack of lubrication. I don't see an easy way to add grease to the relevant parts, though I tried with limited success. Do you just blast the whole track assembly with WD-40 or something similar?