18 speed. Shifter has a lot of play while in gear (slop)

Yes there is a bushing that goes in the bottom of the gear shift. It slides over the stub sticking out of the top plate

 

Like Wore Out said, bushing up top. You can get a repair kit for it.

 

If you have a shorter engine like the C13 there is a linkage rod between the tower your stick comes out of and the tower that drops into the transmission, these get wallowed out and create a lot of side to side slop over time.

They can be repaired by drilling the pin holes out to a larger size or just replacing the rod.

 

I always get these parts from a transmission shop, the dealer seems to have a tough time isolating shift linkage parts.

You may have to buy the whole remote tower as a unit if the slop is internal, I would look for a commercial transmission shop and see what they have on the shelf.

 

They should sell a complete kit which includes gaskets, spring, isolater bushing and maybe the nut and bolt. Not hard to do, just be sure to drain the air before pulling hoses and don't drop anything down inside the trans. Not trying to scare you, just be careful. Hardest part is removing the spring and getting the pin or bolt out of the isolated bushing. Otherwise a piece of cake

 

It's just 4 bolts and the shift tower comes off. I would just get a new shift tower and gasket, and change 3 detent springs while your in there. It's not too hard of a job if you have some mechanical skills, like the other poster said just be careful not to drop anything inside the transmission. The shift tower itself is not too expensive I just bought one for my truck was like 180 bucks I think. Good luck