Had to pull the radiator out of the 620 and to get it out we had to remove the power steering worm housing assembly (item #31) from the tractor. Got everything put back together and now there is a catch in the steering just right of center. Will be going along fine and then all of a sudden it will catch and not want to steer at all. Eventually your able to overcome the catch and all is well again for a while. All we did was remove the four bolts that attach housing to the steering pedestal and remove the steel power steering lines. I did remove the housing last night to look at it and it appears the worm gear is not engaging with the steering gear very well. Only thing I can think of is that the paper shim item #32 was falling apart so I replaced it with another one that I thought was similar thickness that we had. How do I verify what I need for this shim? What do I need to look at here to fix the issue?