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Many people are capable of driving their car for the whole of ownership without ever replacing the gearbox fluid. Although some automobiles advertise lifetime transmission fluid and advise against replacing it to prevent the car from slipping when shifting gears, experts still strongly advise against it.


It is advised to change your gearbox fluid about every 50,000 miles to keep your car in top operating condition. Torque converters are used in automatic transmission automobiles to change gears. Since the torque converter and the gearbox are not physically linked, fluid enables movement to occur between them. By employing fluid pressure and fluid friction, the fluid enables the mechanical spinning of the engine to be transmitted to the gearbox. To ensure that there is no unnecessary buildup or friction in this procedure, you need clean fluid.


The most crucial part of this process is keeping the transmission fluid clean. If you go 150,000 miles without changing the transmission fluid at a moment when your car has become acclimated to that texture of fluid, replacing it then might potentially make your car slide. The converter has likely been operating on soiled transmission fluid, which has a tendency to have more friction, if the fluid is black. At this point, changing the fluid would involve introducing clean fluid to filthy fluid, which would probably start the converter slipping. Changing the transmission fluid at this stage could provide more issues than benefits. The secret is to keep it well-maintained at all times. If the transmission is still functional in this situation, it could even be preferable to leave the transmission fluid alone.

The key here is preventative maintenance; if you wait too long and the transmission fluid is too unclean on a high mileage car, replacing the transmission fluid might result in the transmission having additional issues and, in some situations, could result in the gearbox no longer functioning at all.


  • Every 50,000 miles or so, on average, the transmission fluid should be changed.
  • Do not replace filthy transmission fluid on high mileage cars with new fluid.
  • The key is preventative maintenance.
  • The converter may start to slip when you switch from dirty to clean fluid.
  • Transmissions running on filthy fluid will slide if switched to clean fluid because unclean fluid has higher friction.
  • Experts advise keeping your transmission fluid clean with maintenance even if there is a lifetime fluid warranty.

Just to review the importance of transmission fluid and how it impacts your car. Although the torque converter is fastened to the engine’s flywheel, the torque converter and transmission are not physically linked as they are in a manual car. Instead, fluid dynamics is used to drive the connection between the torque converter and the transmission. Always remain on top of your preventative maintenance to save yourself from future expensive issues!


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