I've got an M50D in my '88. It shifts cleanly and well up through all the gears - i'm ignoring the bad 2'nd gear syncro. If I downshift from 4th to 3rd, it feels like the shifter is in peanut butter. It takes a pretty good shove to get into 3rd from 4th and it's just really slow and if it's cold out it might grind a little. The ATF is topped up and new. I've got the good freeze plugs in the shifter rail holes. Any ideas as to what my problem might be??