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How do I change the Transmission Fluid

Thanks StealthV for this entire procedure

1. Items Required:
  • -- Four quarts of Dextron III Automatic Transmission Fluid (for mine I used Mobil1 ATF).
  • -- Fluid pump (make sure the threads are big enough for the Mobil1 bottle) or a suction gun would also work well
  • -- Oil drain pan
  • -- Set of Rhino ramps or equivalent
  • -- 7/8" wrench
  • -- 3/8" ratchet
  • -- Roll of teflon tape
  • -- Creeper to roll under car
  • -- Troublelight to see in the dark
  • -- One CTS-V (most important part!)






  • 2. Before the oil change, drive at least 10-15 miles to warm the transmission fluid up to at least 150 degrees.
    NOTE: While working under the car, the engine, transmission and exhaust will be extremely hot. Be careful, safety first!

  • 3. With the V safely supported, remove the fill plug on the driver's side of the transmission with the 3/8" ratchet. The fill plug is half-way up the side of the transmission, near the orange "Use Dextron III ATF Only" sticker and CAGS harness.

  • 4. On the passenger side of the V, locate the transmission temperature sensor. It is located on the RH side at the lower rear of the transmission. Disconnect the transmission temperature sensor harness and place the end of the harness behind the transmission's serial number tag to prevent the harness from being melted on the hot exhaust pipe.



  • 5. Slide the oil drain pan under the V and with the 7/8" wrench, remove the temperature sensor.
    NOTE: Caution! Hot oil will come out quickly and also splash on the passenger side exhaust pipe!



  • 6. While the fluid is draining, clean up the temperature sensor.

  • 7. Apply several wraps of teflon tape around the threads of the sensor. Make sure to wrap it the correct direction. Suggest holding the tape in your left hand, the sensor in your right. Place the tape on top of the sensor threads and rotate the sensor clockwise with your right hand. This will put the tape on in the same direction as the threads are cut.

  • 8. Once the fluid is done draining, clean up the transmission of any fluid that may have dripped out around the hole.

  • 9. Thread in the temperature sensor and tighten until it is just snug with the 7/8" wrench.

  • 10. Reconnect the temperature sensor harness.

  • 11. Clean the fill plug and wrap with teflon tape, similar to step 7.

  • 12. Use a fluid pump (or a suction gun) to pump the fluid into the fill hole on the driver's side.





  • 13. Fill the transmission more slowly when you get about half way through your 4th quart of fluid. Continue to fill until fluid begins to run out of the fill hole. Here's the puddle of fluid I had on the floor after "knowing" it was full.

  • 14. Insert the plug and tighten until just snug with the 3/8" ratchet.

  • 15. Clean up your mess, safely lower the V and take it for a spin and enjoy the knowledge that for not much money, you've done your transmission a favor! V
  • 16. Here's the comparison in color between the factory fill and the Mobil1. Hate to see what this would look like after 100,000 miles since GM says it is "filled for life."



    Addition from Dreamin:
    FWIW, the technical specialists / guru's on the Z6 forum advise waiting until 5000 miles before switching to *synthetic* tranny fluid, to make sure the syncho's are fully broken-in.
    here are some Fluid Specifications:


    Also: And here is a "zoomed-out" pic showing both fill (above Dextron III sticker) and drain plugs (lower right of pic). Note the exposed threads on the plugs (factory orange thread compound)... as posted, "tighten until snug"... no need to waste on the plugs.








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