Morgan Plus 8s from 1975 to the early 1990s were fitted with a wide-track Salisbury 7HA with a limited slip differential (LSD).
It sounds potentially that the LSD's clutch plates are sticking/grabbing, possibly worn or even that the diffs planet gears are breaking up. The latter happens if heavy standing starts are used. Mine went in this fashion competing in an autotest on tarmac; since then I have restricted myself to autotests on grass. Too much power is applied at slow speeds when turning causes excess strain on the diff.
The 7HA axles could be a tad marginal used in Plus 8s but not desperately or notoriously so.
LSD oil must be used in this axle. Castrol Hypoid LS or Castrol's competition spec Product B373. Under no circumstances use an oil additive designed to reduce wear or reduce friction or noise.
Quaife used to, perhaps still do manufacture an LSD unit for the 7HA that does away with the clutch plates.
Billy Bellinger in the UK specialises in rebuilding Salisbury axles. I'm unsure of cars exported to Australia with 7HA axles. I believe early Reliant Scimiters were fitted with 7HAs.
I suggest that you try and get a better diagnosis from someone who understands diffs and LSDs before you start assuming the worst. A 'normal' garage won't be much help.
I trust that this helps.
