More problems with the internal parts.Some parts may malfunction
and require replacement.
U can,of course,replace them but since there's so much parts
inside the engine,replacing them may be heavy on your wallet.Thats
why some people opt to overhaul(replace) the engine.Of course,the
latter is more expensive but its all up to you which way you want
to go by - Short or long term solution
Anyway,forget about revving past redline for automatic cars(with
exception of sports cars of course).The ECU will shift to the next
gear whether you want or not.Even in semi-manual mode(Porsche's
Tiptronic),the ECU will also kick in at redline.
For some "cheap" japanese automatic(i.e Nissan Sunny etc),forget
about trying with the single mode selection(Gear 1,Gear 2).It wont
upshift automatically(since its at that mode) and instead you will
feel the speed-limiter effect as the ECU cut off fuel.