Transmission slipping

[Mikesx3]

2005 E83 3.0 149xxx I've noticed occasional transmission slipping for a month or so that has gotten worse in the last few days. Usually at highway speeds and sometimes while accelerating. Is there anything I can do or do I just wait for the inevitable? I know there's a lot of debate on changing fluid and filter.

[X3456]

Ive never used them but there are transmission fluid additives...
Have you considered simply changing the fluid itself?

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[dukedkt442]

Change the fluid/filter, and change the fluid again after a few hundred miles, and again a third time. Each drain only removes about half the fluid.

On the final drain/fill, pour in a bottle of Lubegard Red; it'll restore the friction between the worn clutch packs but not harm them or the solenoids. I use it on every automatic transmission I service and have had nothing but great results. I successfully rehabbed the trans in my 150k mile F150 that never had its fluid changed using the above process.

I forget what the drain pan looks like on the 5 speed, but on the 6 speed BMW used a small (8mm) recessed Allen-style drain plug; if yours is the same, toss it and pick up a proper GM drain plug (14mm hex) to make your drain/fills easier. You may have to cut the un-threaded end off for filter clearance.