I have an 01 truck with the nv5600 transmission and 150000 mi I was replacing my clutch so I decided to rebuild the trans while I was at it,, I put it all back together and 1,2,3,4-6,r all shifted perfectly and smooth but I couldn’t get it into 5th occasionally I could get it in 5th just a little but when I let the clutch out it would kick out and grind I’m thinking it’s something in the shift rails assembly I took it back out can’t find anything wrong I did add a endplay shim to tho counter shaft cause there was a little to much play is there anyone that could help me out I would appreciate it very much also I don’t think the correct fluids are much of a problem for anyone but I used synchromesh from my cousin who owns Blake’s diesel care so I’m pretty sure it’s the better option

Is it possible if the counter shaft is not properly shimmed the gear on the counter shaft could hit the 5/6 shift fork and pop it out ?