Won't Go into R or P when cold, Linkage?

1994 E320 Sedan. 144500 miles. Car runs well overall. When car is cold in cold weather months, if I drive just a mile and try to park, I have to leave it in neutral and the gear lever will not go into Park or Reverse. Today I had to wait 15 minutes until the engine was near 80 C as I forgot and parked in a spot where I could not drive forward. Once the car or transy warms up, after a few tries, it works and all is fine for the rest of the day. Is this a linkage problem? Seemed to happen after I changed the gear lever out to a zebrano wood one in March 2010. Only happens in the cold weather.