Hi, my newly rebuilt 5 speed shifts rough/grinding when cold, as though the gears arent fully synchronizing. After its warmed up it shifts smooth as can be. Its full of new gl5 80-90w. I've only had it in and running for 3 weeks in my daily driver pickup. Could this be a viscosity issue? What else could be causing this? thanks for the help!!!

the linkage could be off just a LITTLE bit.. that reminds me of my problem i had. I had to replace the clutch fork and z-bar bracket.

Are you sure the clutch is releasing all of the way?

What kind of 5speed? All most all of the newer ones use Syncromesh or ATF, not regular gear oil. Sure you have the right oil?

wanarace, i was thinking the same thing.
my tremec 6 speed uses ATF.
david

I changed out the gear oil for synthetic esl and problem went away immediately. almost scary to feel it change that fast as I was shifting through the gears.