How can this be done? Do I have to take it to a shop, or can I do it myself?

Last time I did it on my Regal, I simply put a fluid pump hose down into the dipstick tube and sucked out a gallon, and replaced a gallon. I figured I'll change the filter the next time, along with retrofittina drain plug.

For some reason, I couldn't find a transmission dipstick on the Bonneville, but I would imagine that fluid has to be changed at some point.

Give Venom or one of the other GXP owners a chance to chime in here to see if there is anything about the GXP that makes it any more difficult.

Post edited to remove info not pertaining to the GXP so that it doesn't confuse or cause a problem. GXP Venom.

Bump for one of the GXP guys to tell us if a tranny fluid and filter change is any more difficult on a GXP compared to a 3.8.

You can't get to all the fluid in any manner other than as listed below. A tube wont get yopu anywhere. The 4T80e has two chambers to drain, read on please.

The pan is as easy to get to,The 4T80 is quite a different animal. You can't change the filter by dropping the bottom pan. That is in the side pan and only done when overhauling the tranny out of the car. There are two scavenger screens to replace under the pan. Right/Left Here'* a rundown I lifted.

1. Place a drain pan under the transmission bottom pan in order to catch the fluid. Important: Removing the bottom pan on the HYDRA-MATIC 4T80-E only partially drains the transmission fluid. The remaining fluid is held in the side cover and the torque converter. Removing the drain plug in the case after removal of the bottom pan will drain fluid from the side cover. You do not need to drain the torque converter during most service procedures.
2. Loosen the bottom pan bolts. Drain any fluid in the pan.
3. Remove the drain plug in the transmission case.

1. Remove the bottom pan, the pan bolts, and the seal.

1. Remove the left and the right scavenger screens. Important: The bottom pan seal is NOT reusable. Replace the pan seal with a new part after removing the pan for any service.
2. Inspect the following parts for the conditions cited:

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  • The scavenger screen lip seals in the transmission case.Check for nicks or cuts. If damaged, replace.
  • The bottom pan and the transmission case for dents or nicks in the sealing surfaces. If damaged, replace.
  • The bolts for damaged threads. If damaged, replace. For proper sealing, the bottom pan and the case sealing surfaces must be clean and dry. In order to maintain proper bolt torque, the bolts and the tapped holes in the case must be clean and dry.

Installation Procedure

1. Install the drain plug in the transmission case.

1. Install new left and right scavenger screens.

1. Install the bottom pan and a new seal. Finger tighten the bolts.

1. Tighten each of the 16 bolts 3 times in sequence shown.
   MAYBE SOMEONE HERE WITH AN ALL DATA ACCOUNT CAN POST THE SEQUENCE

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  • 1st Time: Tighten the pan bolts to 3 Nm (27 inch lbs.) .
  • 2nd Time: Tighten the pan bolts to 6 Nm (53 inch lbs.) .
  • 3rd Time: Tighten the pan bolts to 12 Nm (106 inch lbs.) .

1. Lower the vehicle.
2. Add DEXRON(R) -III transmission fluid as required. Refer to Specifications.

Wow. Glad I asked. Thanks for the detail Venom.

LOL! Lets keep in mind the GXP is a Caddy with a Pontiac wrapper.

I'll try to come up with a procedure for this when I have some extra time.

All it needs is the Torque Sequence Dan. And we can polish it and send it to TI.

I'll try to check that tonight. Generally it'* a cross pattern. But will find out for sure.

Nice post, great info- didn't know how different the trans are from the 485.