4 Then there's always the one joint that just won't come loose. We're applying heat to the trunnion while the vise applies pressure to the joint itself. A FEW WORDS OF CAUTION: if the u-joint has a grease fitting, remove it to allow pressure relief as heat builds if it has no fitting. Beware that as pressure builds a small explosion can occur. The ensuing pop can blow the caps off and cause injury if they're not contained.