Automatic gearbox problem

[Fungus]

I've decided to start a new thread as I have now experienced my cars gearbox issue first hand and can provide a more clear picture of what's happening.

I have a 1987 318i automatic, m40 engine. The car runs perfectly and shifts very well at low speed, and the kickdown seems to work as it should.

However, if I accelerate to around 90mph and then let-off, it will downshifts heavily until it reaches first gear-not ideal at high speed. I knocked the car into neutral when this happened and slowed down. The gearbox then continues to work perfectly at lower speeds.

I am told that this could be because of the 17" wheels but I really can't see how that would affect it. Before I bought the car, a new kickdown cable was installed- could the problem be due to poor adjustment?

Thanks