I've read that gearboxes in the BA Falcon are prone to engine coolant entering in to the gearbox at around 170,000 km. Is there any way to prevent this occurring, and does it happen to the BF model as well?
It can happen at any time, it doesn't have to be at 170,000 km. It happens when the transmission oil cooler, which is in the radiator bottom tank, fails and allows engine coolant to enter the transmission fluid stream. It's common with the BA and BF models, but not the BFII, which had an external transmission fluid cooler to overcome the problem. The only real way of ensuring it doesn't happen is to fit an external transmission cooler and bypass the one in the radiator.