As someone who has been in and around the transmission business for 33+ years, I am often asked when the best time is to service or change the fluid in a transmission and what is included in the service.
Good transmission maintenance is just as important as good maintenance is for your engine oil, brakes or any other part of your car. The likelihood of a failure to any part of your car is greatly reduced by proper maintenance and your transmission is no different.
That said, I think it is important to address a common rumor about transmission fluid changes that is often asked- Is is true there are times on a used car or truck when the transmission fluid should NOT be changed?
Exchanging or replacing your transmission fluid will NOT cause a problem with your transmission, but it can definitely uncover an already existing problem that leads to an immediate or sudden failure.
If the fluid has never been changed on a high mileage vehicle that starts showing signs of not working properly, then a transmission fluid change won’t fix the problem. It could, however, make it a whole lot worse very quickly if not right away.
For example, if your engine starts running poorly you wouldn’t change the oil and expect the issue to be fixed. Changing the oil in your engine is strictly proper maintenance and does not immediately fix anything. Therefore, the same is true for your transmission.
Transmission fluid is high in detergent and that old, dirty contaminated fluid might be the only thing allowing it to still operate. By putting new highly detergent transmission fluid into a transmission with burnt, contaminated or varnished fluid can clean and flush all of the loose material to allow your transmission to work properly down into the sump and therefore uncover an already existing problem.
In fact, I have seen situations of customers insisting on changing the fluid (against the technician’s recommendations) and their car wouldn’t even back up off the lift.
This is why we do a thorough check of your transmission to very that a fluid service is right for your car. This is done by performing a free multi-point inspection. This allows us to confirm that we are performing the right service for your car. If we find additional issues, we can then make other recommendations to our customers that address the issues we find.