You probably have the plug in the bottom end of the housing too tight. It should only be tight enought to stop any up and down movement of the steering column, but not tight enough to cause any binding. The "play" is adjusted with the cam follower, the stud in the side plate that has the lock nut. If it has been overtightened, it will also cause the same problem. The inner end of it is tapered, and rides in the slot in the worm on the end of the steering shaft. That tapered end will have flat spots worn on it which causes the play. You can sometime turn it 90 degrees to an unworn spot and get by, but it should have been replaced when the bearings were. New ones are available, but are about $20 which seems high for a hardened, tapered stud. You can also try to true up the one you have if you have a lathe or maybe a drill press. A new one should be tightened down until all the play is removed, but not enough to cause any binding. Because of wear on the worm gear, you may not be able to get all the play out, but it will remove most of it. The side plate has to come off to remove the cam follower, because it is threaded into the side plate from the inside, and is not threaded the full length.