Drivetrain Clunk

[lightfoot]

Replaced the u-joints over the weekend and whala, problem resolved. BUT WHY???? The old u-joints looked fine, no apparent wear on any of the needle bearings, no rust, plenty of grease, nothing felt loose, so why would a new set of u-joints make the clunking sound go away?

[Madman]

U-joints are a replacable wearing surface, wear over the years, which may be invisible to the naked eye, may cause a few thousandth of clerance and you get a clunk under load. A few thousandth per ujoint add up. If your clunk went away, as they say in the land down under "Good on ya, Mate!"

[Mancar1]

[chad67]

It doesn't take as much movement as you think to make a pretty noticeable clunk.

[BobbyFord]

Glad you got it fixed.

[lightfoot]

Look what I found browsing the TSB link.
Article 1302 - Driveline "Clunk" or "Snap"
(1965-1968 F-100-F-350; P-350-P-500; P-3500-P-5000; E-100-300)

So I believe I replaced the u-joints for nothing because when I had the driveshaft out I cleaned and greased the front spline, and according to the TSB lack of lubrication on the spline was the cause of the clunk on 1968 F100’s.