The Official 356Talk Forum

With car jacked up at rear and handbrake off and in neutral , what sort of noises should it make when rotating either wheel by hand , standard ie slippy diff
How much slack should there be ?
Can you analyse noises to pinpoint problems ?

Footnote - one upon a time when I used to drive fast in a more modern Porsche (the 1992 964RS now legally available to use in USA) the limited slip diff would make a terrible noise like cement mixer loaded with tin cans when reversing slowly.....'they all do that sir '

Jack up the wheel in question ( I am assuming you have drum brake cars) look through the hole where you adjust brakes with a flashlight. I would suspect there is a small stone that found its way into the drum.

Either that, or with the wheel off the ground, hold a yardstick against your ear and the other end against the trans case near the axle boot flange and listen for the inner end of the axle/trunnion blocks rattling when rotating the wheel. If you can hear localized noises, it could be a number of things involving the diff carrier and related components.

Jacked up with drooping axles probably adds to the noises. Turning one wheel so the spider gears rotate usually doesn’t sound fantastic on any car, and will show a surprising amount of free play, as if the ring and pinion were set to 10mm backlash.

Pull the drums, and see what is going on. It can be many things, like a broken "Beehive" spring. Plus others. Look for tell tail scrapes on the drum. ..............Jim.

JohnLiles wrote: ↑Thu Jun 23, 2022 7:14 am With car jacked up at rear and handbrake off and in neutral , what sort of noises should it make when rotating either wheel by hand , standard ie slippy diff...

As Martin said, with the car jacked up in the rear the axles will drop to extreme angles inside the differential, angles they weren't designed to operate at.
Just be concerned about noises in normal operating conditions, or if you find metallic glitter or metal bits in the gear oil.

Try changing the jack point. I.e. lift that wheel off the ground by jacking under the wheel hub or lower shock mount. You can still spin the wheel but everything will be loaded as normal.