unfortunately the answer to that is as wide as an ocean.
Standard gearbox's if untouched are anything between 13 - 17 years old and are getting pretty tired now. Standard box's have often let go on standard cars, it all depends on how it's been treated through out it's life.
I have had a standard box live for 2 years on 380 bhp, no launching and treated with mechanical sympathy but then all of a sudden 3rd gear would strip.
The only way to have some sort of advantage is to have the box rebuilt professionally with all new bearings, then use a good oil like Silkolene syntran 5 or some Redline shockproof 75W90.
Regrettably there is no sure fire way to make it 100% safe, you can do your best by rebuilding it or part with some hard earned money and go the Quaife route for some extra insurance.
Steve
