Posted by Glen
on 11/30/2008, 4:03 pm
65.10.72.23
Since u-joints are a hot topic lately, I just want to mention a few more points...
Re vibrations, u-joints are just one of a number of things that will cause this problem.
It's easy to tell if a joint is worn out, clunk-clunk or worse, but it isn't possible to tell if it is stiff/binding up, without removing the shaft & physically checking it in both directions.
Look for signs of the cups turning in the yokes, fresh metal witness marks around the circlip, and/or rust "dust".
When fitting new u-joints-
As always, quality is important. I try to use Hardy-Spicer.
Clean & deburr the yoke holes & circlip grooves.
Fit the cross with the lube hole oriented so that it's loaded in compression when under power (not that important with our low hp cars but still good procedure).
The circlips will usually be stamped, having a sharp side & a rounded side. It's best to fit the sharp edge facing out so it gets a good bite.
If you get one with tight (axially) cups when fitted, you can gain a few thou by reversing the clips ie rounded side out.
The cups have to be a snug press fit in the yokes. If the cup seems to be slightly loose, but the yoke isn't worn, a few drops of "loctite blue" is you friend
After all 4 cups & clips are fitted, the cups need to be "back-seated" in the yokes. Just hold the flange in one hand, or set the side of the yokes between the vise jaws, and smack the end of each yoke in turn with a leather or brass mallet. This sets the cup back against the circlip & gets rid of the axial preload that results from them being pressed in.
When fitted there should not be any more than the slightest bit of stiffness.
Another thing to keep in mind when servicing driveshafts/u-joints, if the sliding yoke is removed, it must be refitted with the yokes on either end lined up in the same plane. If they are "out of phase" it will cause the shaft to vibrate.
Driveshaft balance issues aren't that common, but not unusual either, and ARE a PITA to diagnose...
Just a few thoughts, not an answer to any particular problem...
Glen
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