My T5 Rebuild Problem Help!

I bought a rebuild kit. All new sliders. Input shaft and third gear.
I'm pretty sure I put the fifth gear slider on right. When the engine is off it goes into fifth pretty smoothly.

The trans is from an 88, so I used what was recommended from auto parts store. I don't remember what it was.

I just found this on another thread.

T5 grind into 5th problem

Dragging this back from the dead because I had the same problem and fixed it. I rebuilt my T5 (1990 305 model, WC) which included replacing the 5th gear brass syncro. yes there is one. Freshly rebuilt it would grind going into 5th over 2000 rpm. I discussed the problem with two transmission shops and they both told me the same thing, the cone the brass syncro ring runs against on the 5th gear needs to be "prepped" when rebuilding. It becomes highly polished over time and the syncro will no longer grab on it. One shop said to use 120 grit emery paper and the other said to use 600 grit emery paper. I took mine back apart and rubbed 320 grit emery paper across the face of the cone to remove the shine, replaced the brass syncro ring just in case, and reassembled it. Now it works great no grinding at all.