ok this one for me is a head scratcher.

whats happening is i'm loosing 5th gear, and 3rd gets mushy to go in.
The other day i was driving down the road and whipped a U-Turn and all of a sudden i could not get to go into 5th, it was like something was in the way inside the tranny. so i let it sit over night and the next day it was fine, went through all the gears no problem. this has been a reoccurring issue and it always seems to fix it self. WTF??? any help here.

info about the car 1992 SC300, 1j swap with r145 from a 1992 soarer, i had to get the shifter extended to fit the SC.