I bought 2008 Toyota Camry with 136000km. They told me to replace the gearbox oil and filter-but many people worn me that the gearbox will get damage if I change the oil &filter? Please help, what should I do ? Thanks.
Toyota does not list a service interval for servicing the fluid and filter. That being said, if you are not having any issues with the transmission, changing the fluid and the filter will not damage anything.
If the fluid is black and contains particles in it already, changing the fluid and filter won't damage anything that is not already broken, but you may experience some shifting issues after the fluid has been changed. There is the risk of it not shifting at all after being serviced, although this is usually only an issue if the transmission was failing before the service was attempted.
If you are going to service the transmission and filter, do so on a regular basis (30,000-60,000 miles depending on driving conditions). Otherwise, leave it alone and change the fluid when you replace the transmission.