When is it time to change your transmission Fluid?

There are a lot of beliefs and guesses about when you need to change your transmission fluid. Your Original equipment maintenance books will have that information in them to guide you. These questions come to us on a regular basis with older style transmissions. They also ask what types of fluids they can use with their transmission.

First let’s talk about when is it OK to change your transmission fluid in the older 2 speed and 3 speed transmissions. Transmission fluids are sealed and not exposed to the combustion like the engine oils are. So, this means that the fluids are going to stay cleaner for a longer period. Fluids are designed to do a lot of things for the transmission. It obviously lubricates the system. It also conditions the clutches and O-rings in the valve body. It also acts as a coolant for the transmission with the flow of the fluid through the transmission’s system. We highly recommend that you do use OE fluids and or direct replacements because they are designed for that application or transmission. 40,000 miles is a great time to start thinking about changing the transmission fluids for these types of transmissions. If you exceed 60,000 miles depending on how the vehicle is used as to the condition of fluid and clutches you might want to think twice before making modifications or changing too much. By changing the fluids far beyond what is recommended you can do more harm than good. You would be better off rebuilding the whole transmission and going with all new fluids to prevent potentially fatal damage to the transmission and torque converter. If it has been too long in between fluid & filter changes, then let it go. DO NOT change the fluid. The question is WHY? The answer to this is that the new fluids have fresh detergents and additives that condition the parts in it that will try to do its job and clean everything too good. This can quickly clog the filter and break up or should I say free up trapped contaminates throughout the transmission & torque converter system and allow them to cause damage to the transmission. I would suggest 4 years or 40,000 miles whichever comes first. Yes, even if the vehicle does not get more than a few hundred miles a year on it. Change the fluid. These fluids are designed to go from hot too cold repeatedly and conditions each of the parts accordingly. If they are left sitting over time the fluid, simply goes bad and loses the ability to handle the high demands of the transmission.

There are a lot of variables involved in how well the fluid holds up that must be factored in. How you drive and the areas weather will make a difference. Open HI way Vs stop and go traffic makes a difference. Stick with the manufacturers recommendations as best as you can. If your vehicle is still stock this will work fine and keep you going. If you have made modifications to the vehicle or load it down quite often then your fluid would need to be changed more often.

As you make modifications to the vehicle for more power, this translates into more stress or torque through the transmission increasing the operating temperature. As we learned in earlier posts this will also effect the stall in the torque converter. If changing the power and or torque converter you may just want to rebuild the transmission to insure proper output without failure.  

The transmission and torque converter is a hydraulic system and must be kept clean. There are more than 200 parts in a transmission that all have to work together. There are no short cuts, just preventative maintenance.

Happy motoring !