Hi, Im trying to remove my transmition so I can change the clutch in my 81 GMC 3/4 ton 4x4, but I can't figure out how to take the shifter out. I tried pressing down on the slotted collar plate and rotating counter clockwise, but it will only turn about 45 degrees then it stops. What am I missing here? Do I need to remove the entire top cover of the tranny? Any help would be appreciated. Thanks.