Transmission

I have a 1988 cavalier with a 2.8 motor and a 5 speed tranny with 134,000 kl. The problem is the shifter won`t move side to side to shift gears unless I warm up the car for 1/2 hour.I changed the fluid to synthetic oil and oiled the linkage and it never made any difference. The weather here is minus 20. Is there any other things I could check

thank you