what can cause my 5 speed to lightly grind when shiting to 3rd or 5th when reving over 3k

 

synchros are prolly going out..

try changing your trany Fluid with some Honda MTF from the dealership. You should be changing your trany fluid regularly.. (every other oil change or so)

GM Synchromesh is also really good and helping smooth the gears. It's expensive and difficult to find, but it works good.