I did the Auto-Rx transmission treatment about 18 months ago and am about 20,000 miles afterwards.  Over my winter break (December), I am planning on dropping my valve body and performing a J-Mod on my 4R70W automatic.  This just entails drilling some holes in the separator plate, removing some springs, and installing a new O/D servo spring.

Since I will have the entire valve body removed and will be draining and refilling with new fluid, should I do the Auto-Rx treatment beforehand?  To date there are no leaks, the ATF is still a bright, clean red color, and no problems shifting or anything.  I don't know if it's be a waste of an application since I will be cleaning everything visible, anyway.

Rich

Sorry I missed this. YES. Any blackened bores should be cleaned up nicely. You probably won't have access to a carb cleaner bucket (years ago we had what was called a GUNK tank for trans parts) to soak it in. I'm not up on the more contemporary automatics, but I assume you still have the worm farm inside the valve body.

By all means run 6 oz through the thing before you pull it down. It will save you some time.