Can I just drain some at the drain plug and refill? What else is involved?

 

Yes, you can. You'll need to remove the aero panel to access the drain plug.

 

You'll need to get the transmission up to operating temperature and run it through some gars before you check/top off the fluid. The details are in the service manual, perhaps someone will post them.

 

Below is a procedure for the "Fluid Level Check". The Service Manual that techs use is updated regularly and procedures are subject to change. I like to recommend that anyone this actually going to do this stuff get an official copy from Helm inc. Note the procedure indicates use of "Fuchs TITAN EG FFL-4 TREMEC transmission fluid ". That has appeared in several iterations of the service manual, even though we know that the dealer use GM ACDelco DCTF FFL-4. I'm not saying the Fuch product is the same or different - but I will be using the Delco product.

This following procedure is performed AFTER the fluid has been drained, and then filled to the fill plug level:Transmission Fluid Level and Condition Check
Fluid Level Check ProcedureWarning: The transmission fluid level must be checked when the transmission fluid temperature (TFT) is between 20–40°C (68–104°F). If the TFT is not within this range, either idle or brake torque the vehicle to raise the fluid temperature, or shut off the vehicle to allow the fluid to cool as required. Setting the fluid level with a TFT outside this range will result in either an under or over-filled transmission. TFT greater than 40°C=under-filled, TFT less than 20°C=over-filled. An under-filled transmission will cause premature component wear or damage. An over-filled transmission will cause fluid to discharge out the vent tube, possibly causing a fire that may result in serious bodily injury or severe vehicle damage, fluid foaming, or pump cavitation.

1. Start and idle the engine with the A/C turned off.
2. Run vehicle for 3 to 5 minutes while selecting drive and reverse to fill the clutch circuits. To properly fill the circuits place foot on brake, shift into drive for 30 to 45 seconds then shift into reverse for 30 to 45 seconds then repeat.
3. Stop the engine and perform the following actions within 5 minutes after stopping the engine.
4. Raise the vehicle on a hoist. The vehicle must be level with the shift selector in PARK range. Lifting and Jacking the Vehicle
5. Note: To avoid rounding of the transmission oil filler plug, it is recommended using an appropriate 6 point metric socket or wrench.
   
   Caution: Use Fuchs TITAN EG FFL-4 TREMEC transmission fluid only. Failure to use the proper fluid may result in transmission internal damage. [My note - use Delco DCTF FFL-4]
   
   Note:
6. During transmission manufacturing, the fluid is filled by volume and therefore, it could have a fluid level that is approximately 13mm (0.5 in) below the transmission oil filler plug.
7. If more than 1 liter (1.06 quarts) of fluid drains from the transmission, the transmission may have been previously filled for track use.
8. Note: To avoid rounding of the transmission oil filler plug, it is recommended using an appropriate 6 point metric socket or wrench.
9. Place suitable drain pan under transmission.
10. Transmission Oil Filler Plug (1) » Remove — Transmission Oil Filler or Drain Plug Replacement
11. Fill or drain oil until oil level is at the bottom edge of the fill opening.
12. Transmission Oil Filler Plug (1) » Install — Transmission Oil Filler or Drain Plug Replacement

 

Thank you, not something I can do in the garage.

 

This is an interesting statement:

Since GM advises you can "over-fill" by 2 quarts without any problem. This reads like it was copied from the procedure from some other car.

 

My dealer allowed me to provide the fluid and filter which was a substantial savings. They charged me a flat $300 to perform the flush, drain, and track refill. I was able to purchase a filter from Rock Auto for $110, and 11 quarts of fluid cost me $298 from an online GM dealer.

 

That is interesting isn't it? There is an additional procedure for Transmission Fluid Fill Procedure (Track Use). The first step in that procedure is a call to the same Transmission Fluid Level and Condition Check (that includes the caution about overfilling). That track fill procedure is a stand-alone procedure - not in the context of a drain and fill. But it includes first the step to make sure the level is correct for the normal fill plug, before adding the 2 liters. Seems like a good idea.

 

Very jealous that your dealer allowed this. Unthinkable here in Nazifornia.

 

A friend told me that Rydell Chevrolet in Northridge "Nazifornia" (as you put it) allowed him to supply his own fluid. So, not so unthinkable.