Hope some one can help with this. I have a 1994 C-1500 2wd with a 4.3L engine and 4L60E transmission that only has R, D and OD. 1st gear stopped working but allowed manually shifting between 2nd, D and OD. Then 2nd gear stopped working and it only has D and OD no matter if the shifter is in 1, 2 or D. There was no noise or slipping before 1st & 2nd stopped working. It will shift automatically between D & OD when at highway speeds. Fluid level is fine and there are no codes (OBD1) showing any transmission problem. Anyone have an idea what is going on? Thanks, James.