My wife had been complaining for a while about hard shifting into reverse and 5th gear. I had adjusted the linkage a couple of times and it seemed better but I finally determined to replace the shift cables with new GM ones. The old side to side cable (white ends and on left side of shifter and bottom lever of trans was very hard to move, as others here have found. The issue on our 125k mile SS is the cable had been rubbing on the gas vent line from gas tank to up by pvc entrance on intake. I have a picture of the damage below. You may want to check yours for rubbing on that line or something else and protect it there. The rubbing went thru the case and allowed water to rust the inside of the cable housing. Would have saved $100 and a bear of a job if I had seen it before

.

 

Did you find new shift cables?

 

Yes, bought them from ZZ performance, but they are also available from dealer I discovered later. In GM Sealed packaging and with same part number that was on original cable set. Date was 2020 on package

 

Thanks for the update and confirming the ZZP cables fit!