Some people never change their transmission fluid often enough and then eventually it may lead to transmission problems and transmission failure.
Most people think to change their engine oil to keep their engine working properly and extend the life of their engine but most people never really think to change the transmission fluid which helps keep their vehicle moving down the road.
I've known people that never change the transmission fluid and they have no problem with the vehicle however I've also had people bring me vehicles with transmission problems and even complete transmission failure due to never changing the transmission fluid.
Most manufactures recommend that you change transmission fluid every 30,000 to 60,000 miles and me personally I change my transmission fluid after every 30,000 miles just to keep my transmission working properly.
It's cheaper to change the transmission fluid and filter often than it is to change the entire transmission.
Having another transmission installed can cost from $2,000.00 to $6,000.00 depending on the make and model of vehicle.
I have a transmission going good in a truck that has 500,000 miles on it and I've changed the transmission fluid and filter every 30,000 miles.