Differential problems. The car is running a 4:9 diff out of a Nissan vanette with a LSD.
This Sunny has been highly modified insofar as the engine has been bored and stroked to get capacity from 1400CC to nearly 1600CC.
Car runs an Escort competition rocket box which is fantastic and strong.
Diff is LSD 4:9 Vanette Diff as per note above. Sure I have had problems with the Diff, however they are very cheap to buy and replace (AUD50.00)
This car, in its present guise, is incredibly quick and very very strong.
My Brother had one of these. It had one major flaw, it didn't actually start, otherwise it was great.
Having driven Datsun Sunnies for the last 20 years, and owning at present three registered cars, yes I have children, their reliability is superb. Though I am well aware of their design flaws, as I have owned over 8 in 20 years. Rust has been always a problem, especially the cross chassis rail member affecting their caster.
Great car. Did you have much to do to get the van diff in?