John,
I'm not so sure you can say u-joints are in decent shape just by seeing them
and checking their tightness. The torque applied to u-joints is tremendous
and that is very difficult to replicate on a bench. I might say near
impossible but someone has probably figured out some way of testing axles
for worn u-joints by applying high torque loads. So don't rule them out
yet. You've gone this far and unless you absolutely know that the previous
owner replaced them very recently I'd go ahead and replace them anyway.
It's one of the most commonly needed repairs for these cars. And certainly
a whole lot cheaper than being talked into rebuilding the diff!
Whether the splines in your axles are worn or not you may want to consider
the following. As the force of axle rotation is almost always in the
forward direction it is really one side of each spline within the sliding
axle joint that is seeing those forces. By swapping the axles to opposite
sides you reverse the force against the splines and in effect are using
"new" splines that only saw force when the car was in reverse. If the
splines are visibly worn, though, the axle will need to be replaced. Good
used inner and outer axles are available if that is the case.
Diagnosing a differential by feel takes some experience. I'm not sure what
you mean by "wiggling the axle flanges" so I'll add this. This next part is
one of those coordination things that sounds easier than it actually is
until you get the hang of it. With the driveshaft disconnected and rear
axles off of the diff grasp the diff flanges with your two hands and gently
rotate both hands in the same direction back and forth feeling the play in
the diff. As the diff flanges want to move in opposite directions (in
actuality the same rotational clockwise/counterclockwise direction, just on
opposite sides of the diff) the tendency is for your hands to also move in
the direction of each flange. There should be a bit of play there but not
much with the only resistance felt by your hands at the end of rotational
travel in each direction.
I would get a strong light and take a good look up into the diff mounts.
Cracked mounts are not necessarily that obvious.
Greg Dito
CD6250L
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