92 STS difficult going into park

This is a very unusual problem. I am having difficulty going into park. The transmission functions flawlessly in every other aspect. Specifically, if the transmission is put into reverse and then attempted to be put into park it will not budge but if it is placed into neutral or any other gear and moved directly to park it will go with some difficulty. I have completely checked the cable and shifter assemblies for adjustment, binding or wear and have eliminated them. The problem lies within the transmission. I suspect the reverse servo may be the culprit but I have not found this problem on an fault tree in the service manual. Any suggestions would be greatly appreciated.

Dave,
Welcome to AF.
are you sure it isn't the little roll/spring pin in the shifting lever itself.
I've seen many of the STS's with that pin that holds the base of the shifter lever into the cable assembly wear down, and cause the pin to partially slip out of the housing, "binding" the lever from going into "P"ark which is a smaller "entry" on the housing.
I know you said you checked the cable/shifter assembly, and if so, then I am afraid you could be correct about the servo.
GM should have made that a TSB or a recall, but there again, they believe you should come buy a new one in three to five years.
unless you have other issues, and need the trans opened up, I wouldn't go in for this, and just shift down everytime, before up to Park.
labor on this would probably be close to 3-4bills, and you might as well have them change fluid, filter, and anything else while it was in.

hope this helps,
chris
nrt racing