Odd squeal/ squeak sound

[Tea]

Hi all,

This is a long shot as I can't detect where the sound originates and so may be a bit too vague for an answer. Within the last couple of weeks our 1971 traveller has developed a sound that I can only describe as a mild "wobbling" squealing squeak that when sitting in the front seats seems to be coming from the rear of the car, but from the back sounds more like it's all around the underside of the car. I guess it has a similar sound to cycling a push bike with completely flat tyres, only faster. It only starts once the car has had time to get to running temperature, only happens when moving and gets slightly worse with time. The sound neither speeds up nor slows down with increased/ decreased speed and going over bumps doesn't increase the sound either. It doesn't effect how the car drives.

I have given the car a service (it was almost time for this years service anyway) since it started, including greasing all round, brake check, engine oil change, filter change, gearbox oil top up, diff oil top up, carb dash pot top up, etc.

On inspection of all of the suspension the only issue that I can see is slight perishing of the bushes on the rear springs.

Has anyone got a suggestion of what it could be or which part of the car to next investigate. I'm under no illusion that my description gives that much to go on.