The wipers on my restored 1975 HJ Holden Ute shudder across the windscreen on the downward stroke, particularly in light or easing rain. The complete mechanism was restored as best I could to eliminate any wear induced play, plus I've fitted new blade assemblies and a new screen. I've tried RAIN-X, which makes the water bead and run off, but doesn't stop the shuddering. What can I do to eliminate it?
They shuddered when they were new, the problem is that they're not flipping over when they should at the top of the stroke and they're forced back across the windscreen against the grain if you like. Look at the blades and the way they are mounted on the arms and make sure they are free to change angle when they change direction.