Hi I'm thinking about tuning my car. I have a 535d 06 with auto gear. I Just what to know if it happens often that the gearbox breaks down when you chip tune it. I read that the gear box only can handle 600 tourqe ????

 

The Pre-LCI gear box is safe up to 700-800nm max after that it will not take much more stress, The Post-LCI will take much more stress 800nm+ but its best to stick to within the limits if you want the gearbox to last.

Find a reputable tuner if you go this route and you should be fine.