912 S2 Maintenance Manual Line

If your engine is at 1000 hours then I would absolutely pull the gearbox and send it in to be inspected / overhauled. You can not tell the condition of the interior parts just guessing or by just checking the friction torque measurement on the gearbox clutch. It's not just about lead deposits. Parts inside the gearbox wear due to a couple of factors. Plus doing it as preventive maintenance will be a whole lot cheaper than if you have to replace major parts due to unchecked wear. At 1000 hours you will have worn parts that will need replacement. Until a visual inspection is performed it's hard to say how much wear. 

Thank you! Could you tell me how much it cost for the Gear box P/N: 887703? 

Hi Anh,

I see you live in Vietnam. I don't know about overseas cost. Here in the US a standard gearbox inspection and the replacement of a few minor parts is around $850. If you have larger badly worn parts it can climb to $1800 - $4500. The $4500 is for some seriously worn out parts. Common things that get replaced are items like the belleville washers, the delrin thrust washer, bearing and seal and shims. If your gearbox is really worn you may see the items like dog gears and the prop shaft replacement. They will remove the clutch and take it apart for cleaning. So all this kind of depends on what they find after they disassemble it. Most of the time it's just a simple easy inspection with those minor parts if you have taken care of the gearbox. Things that cause excessive wear are things like wrong oil, too much vibration from no carb sync, prop way out of balance, idling too low, low gearbox friction torque, ect... Basically anything that causes unwanted vibration which a mechanic or owner should keep an eye out for and do the normal proper everyday maintenance. .