Squeaky right front axle in 1985 Jackaroo

I have had my 1985 Jackaroo for 3 years now. It infrequently develops a very annoying squeak in the right front axle area, that can be heard by anyone within earshot of the car when it is moving. The squeak occurs when turning or going over a bump, and usually persists for several weeks or even months. It then just stops.

My mechanic is at a loss to correctly diagnose and correct the problem. The last time it happened was after the car had its regular 5,000 km service. When I started to drive the car after the service, the squawk was terrible. I took it back probably 3 times and each time he lubed up the entire area to try to stop the problem - to no avail. He thought it might have been the shocks, so he replaced them. They were apparently the originals, and now I have nice new heavy duty gas shocks - one good outcome (although expensive) as now the Jack is more stable around corners and over bumps. However, this did not address the problem. About 3 months after the squeak started, it has now largely stopped.

Any ideas as to the problem and its solution?

Thanks.