This is what the transmission looked like before being taken apart. Not too bad up top, but you can see a gradual buildup of grime on the lower half.

Think you can delicately remove parts, clean them, and put them back in without cross-contamination from the rest of the case? Think again. Not worth taking chances here. The whole case must be cleaned, inside and out.


So I started by scraping the bulk of the shmoo from the case. Then I set about removing the leftover gasket material from the solenoid pack mating surface. Interestingly, the diff cover, transfer gear cover, and lower pan had all been assembled without the use of actual gaskets. Instead, they had been sealed with gasket-maker. Lovely.

A lot of this was messy work, and I neglected to take pictures of the process. After scraping off the worst of the “mud, blood & beer” (as they say), I took the lightweight aluminum case to a DIY car wash booth. I sprayed down the whole case in degreaser and scrubbed it down with a brush. Once it was clean enough, I hit it with the pressure sprayer (man, I gotta get one of my own someday!).

I then took the case home and immediately blasted it with compressed air to dry it out.


Now, as I mentioned earlier, the bearings and their races were in very good shape, and did not need replacing. Because of this, I left the output races pressed into the case. The case might be aluminum, but those races aren’t, and it’s very important that I do NOT let them rust.

So after drying out the entire case, I took some fresh ATF (+4) and coated the clean steel. Furthermore, I put the entire case into a clean trash bag and placed some moisture absorbent packets inside to help dry out every last drop of moisture and keep it dry until I opened the bag back up.


I left the case and desiccant packets in the closed bag overnight. I then mounted the case back on the stand (after wiping the stand down so that it was nice and clean, too), and covered the whole thing with a trash bag to keep dust out.


Now I’d like to jump right into cleaning all the parts before getting into assembly, but here’s the thing. You see, during my last rebuild (a 4R70W), I had cleaned all the parts and coated them in transmission fluid so that no rust would start forming overnight. But the next day, I pulled back the dust cover to find dead ants all over my workbench. Turns out they’re attracted to ATF. Fearing that a tiny fluid passage would get blocked, I had to re-clean almost everything.

Lesson learned. I now cover the transmission with a trash bag and secure the open end tightly around the post of the engine stand. All parts stay coated in a sheen of old ATF until I’m ready to clean, lubricate, and install them into the case. (Oh, and BTW, I now use a little spare dish of ATF for an ant trap.)

A bungee cord around a rag keeps the bag tightly closed against dust and critters

Next: Assembly, Pt. I...

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