How do you change the transmission fluid in the Model S?

Stephen Leung  this should help you out:

Gearbox Fluid - Front (Remove and Replace)

FRT No: 39300102

Special tool required for this procedure:

SupplierPart NumberDescriptionTesla1054946-00-AFluid Transfer Pan

1. Remove the underhood storage unit (refer to procedure).
2. Release the straps that secure the lower RH section of the acoustic cover around the front drive unit.''Note: Remove only the lower RH section of the cover to access the drain plug.''
3. Set the fluid transfer pan into position beneath the drain plug. Ensure that the pan is level, then route the drain hose between the subframe and front aeroshield so that it will drain into an oil drain pan outside the vehicle.
4. ''Note: Ensure that the oil drain pain is able to hold at least 2 liters of fluid.''

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1. Remove the fill plug (torque 28 Nm).
2. Remove the drain plug and allow all fluid to drain into the transfer pan.''Note: While the fluid is draining, ensure that fluid does not overflow the fluid transfer pan.''
3. Clean and reinstall the drain plug (torque 28 Nm), remove the transfer pan from the vehicle.
4. Fill the drive unit with the correct amount of proper fluid:
   • Use the fluid specified in General Information > Fluids and Capacities > Fluids .
   • Use the amount specified in General Information > Fluids and Capacities > Fluid Capacities .
5. ''Caution: Use exactly the specified amount of fluid. Do not fill to the top of the fill plug.''
6. Install the fill plug (torque 28 Nm).
7. Reinstall the lower RH section of the acoustic cover around the front drive unit.
8. Reinstall all components that were removed for access.
9. Perform a road test.

Gearbox Fluid - Large Rear Drive Unit (Remove and Replace)

FRT No: 40300102

''Warning: If the vehicle has air suspension, activate "Jack" mode on the touchscreen before raising and supporting the vehicle.''

1. Raise and support the vehicle (refer to procedure).''Warning: Do not work on an incorrectly supported vehicle.''
   1. Remove the mid aero shield (refer to procedure).
2. ''Note: The fluid should only be drained when the transmission is warm.''
3. ''Warning: Be careful when draining the fluid; the fluid can be very hot.''
4. Position a container to collect the fluid.
   1. Clean the area around the filler plug.
   2. Remove the filler plug.

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1. Remove the drain plug and allow the liquid to drain into the container.''Note: Allow the fluid to drain completely before continuing this procedure.''

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1. Clean and install the drain plug (torque 28 Nm).
   1. Fill the drive unit with the correct amount of proper fluid:
      • Use the fluid specified in General Information > Fluids and Capacities > Fluids .
      • Use the amount specified in General Information > Fluids and Capacities > Fluid Capacities .
   2. ''Caution: Do not fill to the bottom of the filler plug opening. Use exactly the specified amount of fluid.''
   3. Install the filler plug (torque 28 Nm).
   4. Install the mid aero shield.
   5. Lower the vehicle.

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1. Gearbox Fluid - Small Rear Drive Unit (Remove and Replace)
2. FRT No: 40300402
3. ''Warning: If the vehicle has air suspension, activate "Jack" mode on the touchscreen before raising and supporting the vehicle.''
4. Drain & Refill
   1. Position the vehicle in preparation for raising it, but do not raise it at this time.
   2. Air suspension vehicles only: Depressurize the rear LH air spring (refer to procedure).
   3. Engage "Tow" mode.
   4. Remove the LH rear wheel (refer to procedure).
   5. Remove the mid aero shield (refer to procedure).
   6. Prepare a drain pan to catch the gearbox fluid.
   7. On the LH side of the gearbox, release the drain plug. Allow the fluid to completely drain, then reinstall the drain plug (torque 28 Nm).

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''Caution: Do not attempt to fill the drive unit through the upper plug.''

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1. Remove the LH parking brake caliper (refer to procedure).
   1. Release the bolts that secure the following 3 fasteners to the knuckle:
   2. 
      
2. Upper Link

Toe link

Shock absorber

1. Use a driveshaft extractor to release the axle from the drive unit.
2. Release the axle seal from the drive unit.
3. Slowly fill the gearbox through the axle opening.''Caution: If the gearbox is filled too quickly, fluid will spill out onto the drive unit casing.''
4. ''Note: Use the fluid specified in General Information > Fluids and Capacities > Fluids .''
5. ''Note: Use the amount specified in General Information > Fluids and Capacities > Fluid Capacities .''
6. ''Caution: Use exactly the specified amount of transmission fluid. Do not fill to the top of the axle opening.''

1. Inspect the axle seal for damage and replace if necessary.
   1. When installing the driveshaft into the drive unit:
      • Ensure that the opening of the snap ring is facing towards the bottom of the drive unit.
        • Do not damage or displace the drive unit seal.
        • Verify that the driveshaft is fully seated by carefully pushing it into the drive unit until there is an audible "click" from the snap ring.
      • Reinstall the 3 fasteners to the knuckle.''Caution: Do not fully torque the fasteners at this time; they must be torqued when the vehicle is at ride height.''
      • Reinstall the parking brake caliper.
      • Reinstall the rear LH wheel.
      • Disengage "Tow" mode.
      • Air suspension vehicles only: Repressurize the rear LH air spring (refer to procedure).
      • With the vehicle at ride height, fully torque the 3 fasteners to the knuckle:
        • Upper link (140 Nm)
        • Toe link (130 Nm)
        • Shock absorber (torque 140 Nm)
      • Reinstall the mid aero shield.