Hi John,
Had the same problem on my 4/4. got the same story of WD40. But was told to use it on the spring hangar bushes if possible. This is a touch awkrawd to do on the front leaf spring hangar. However, more importantly, the little bit I got in there did seem to work for a 1000miles or so and then it tended to go by itself.
Hope this helps
Gaz
