Question for someone who has removed and cleaned a transmission.

The plan was to clean the transmission and then spray can paint it grey to look a little like aluminum then mount it back under the truck (2000 Tacoma 2.4L 2WD 5-speed Manual)

It was pretty nasty, being 23 years old and subject to a leaking rear main seal, among other dirty things. Eventually it began to yield to my persistance. It isn't perfect, but. . .

While working on the aluminum surface with a variety of abrasive grits, it was getting fairly nice looking IMO. . . which made me wonder if I might find some clear primer and clear sealer so I could keep the aluminum look, but have it protected from the elements.

Found lots of grey self-etching primers, but nothing clear.

I remembered a product called something like Shark Hide that sounded like it might work, but I haven't found anybody using it for this application. Where that product is mostly used is on the aluminum pontoons of boats. Back when I was reading about using it, it sounded a bit tricky to use, even potentially dangerous.

Surely there are people on here who have R&R their transmissions, and maybe some, maybe most, even cleaned it before putting it back. Among those who did clean it, has anyone been in this situation before, and if so, how did you deal with it?

I'm about ready to just paint it grey like I had planned in the first place, after all it will never be seen, but thought before I do that, give TW people a chance to share what they might know. And if there might be a better place to post this question, to reach that person, please let me know.

 

Just my opinion, but it really doesn't look like the elements have hurt it much in 23 years. Maybe mask off the cast iron in the middle and paint that black. Probably get another 23 out of it.

 

Thanks, soupy1234, that's useful. Hadn't though of doing that, but the cast iron could benefit from some kind of treatment.

The elements haven't hurt it. . . It took a lot of hand work to get it to that point. When it came off it was really nasty. The inside of the bell housing was layers and layers of dark black stuff, which I presumed was oil from a rear main seal leak, and the outside of the transmisson case wasn't much better.

Fyi: getting another 23 out of it. . . it's in the end stage of hand cleaning away horrid thick oil sludge from the top, front, bottom, and then "while I was in there" replacing the rear main seal. I won't know if it is even going to run again until it all goes back together and no seals are leaking, and the cylinders are generating compression. All I know for certain is that it was running when I noticed oil smoke pouring from the engine compartment, from oil dripping onto the exhaust manifold, which led to removing the valve cover, which led to. . . a partial overhaul.

Do you have any thoughts on putting some kind of clear see-through coating vs just spray painting it grey?

 

It's been a long time since I painted an engine or transmission. We usually went with factory colors back then.
I did a quick search for "clear engine paint" and got a few hits on Amazon and one for autozone.

https://search.brave.com/search?q=clear+engine+paint&source=web

https://www.autozone.com/paint-and-body/engine-paint/p/vht-clear-engine-paint-11oz/465393_0_0

$14 Dupli-Color DE1636 Engine Enamel Spray Paint with Ceramic - Clear - 12 oz Aerosol Can

https://www.amazon.com/Dupli-Color-DE1636-Ceramic-Clear-Engine/dp/B000GKEXW0?th=1

 

Thanks again, soupy1234. You did my shopping. You are hired!

Tried your first two links, and the products were nearly identical, and the third was the same as the first,

$14 Dupli-color DE1636 Engine Enamel Spray Paint with Ceramic - Clear - 12 oz Aerosol Can

Dupli-color DE1636. The VHT is a clear gloss enamel engine high temp paint (550F vs Dupli-color's 500F) just like the Dupli-color. Discovered that VHT and Dupli-color both are owned by the Sherwin-Williams Company (another monopoly; yet without knowing that it looks to us consumers like we have two competitors in the auto high temp spray paint marketplace).

Neither of them have primers that are transparent, so I cannot use them and have the aluminum be visible. I chatted with my ChatGPT and learned that "etching" referred to in "self-etching paint primers" is necessary to give the raw metal surface some features on the aluminum surface that the top coat can grab onto. If I cannot get a transparent self-etching primer, GPT suggested I use either phosphoric acid (10 - 20% dilution) or hydrofluoric acid (more dangerous) to do the etching part that the self-etching primer does.

The GPT first claimed that transparent self-etching primers exist, but when I challenged it, it came back asking for forgiveness and told me that it had made a mistake. When I had looked, neither Google or DuckDuck was able to locate a transparent etching primer.

The products you pointed out may or may not work if I do the etch with acid, and the acid is not a "primer", so I will ask one of the product experts. I would think it would be ok, so long as the surface was etched and cleaned and neutralized. And even if they cannot tell me for sure it would last, maybe it would last long enough, whatever that means.

Just for kicks, I will show you the message I left for someone at VHT to answer:

"I need to coat my 23 yo aluminum transmission case for long-term protection, and I want to let the look of the aluminum metal show through, since I have spent a lot of time hand cleaning and sanding the surface, giving it a pleasing look. Neither you nor Dupli-color have a transparent self-etching primer. And I cannot find a transparent self-etching primer anywhere that Google or DuckDuckGo can find.

Instead of a self-etching primer, could I use phosphoric acid to etch the aluminum and then use your gloss clear high temp product on the resultant bare aluminum and still get long-lasting protection? And, if so, do you have any application notes that could help me do this?"

I know for sure that what I want to do has been done by SOMEONE long before I wanted to do it. Nothing is usually left undone in human world, meaning there might be an area somebody could generate a patent, and such opportunities rarely exist. I will let you know what they end up saying. Hope it doesn't take them a long time to get back.

 

I would think that after all the cleaning, brushing, and sanding that your cases would have plenty of surface roughness for the clear coat to grab. The issue with using an acid and then rinsing and neutralizing is probably that the aluminum will immediately form a corrosion layer when air hits it (if I remember my chemistry correctly). Not sure if that matters much for this application.
If you can't find anything suitable, I'd try applying some to the top where it won't show and then hitting it with a brass brush after a couple of days to see if it sticks. Be sure to get it completely degreased.

Or you could paint it with the aluminum color first, then clear-coat it.

 

Thanks for sticking with me, @soupy1234. What you say is concerning. I discussed the detailed chemical reactions with my AI friend and learned that:

"Phosphoric acid is a strong acid capable of reacting with the surface of the aluminum metal. When aluminum reacts with phosphoric acid (H3PO4), several chemical processes occur. When phosphoric acid comes into contact with aluminum, it reacts with the aluminum to form aluminum phosphate (AlP04) and hydrogen gas (H2).

Formation of Aluminum Phosphate: Aluminum phosphate (AlP04) is a white crystalline solid that forms on the surface of the aluminum. This compound can provide a protective layer over the aluminum surface.

Surface Treatment: In the context of etching or treating aluminum, this reaction can be used to selectively remove or modify the surface of the aluminum. The aluminum phosphate formed may alter the surface properties, such as providing corrosion resistance or changing the surface texture.

Role in Etching: In the process of etching, phosphoric acid can dissolve and remove the aluminum oxide layer (Al2O3) present on the surface of aluminum. The reaction with aluminum forms aluminum phosphate, which may contribute to the etching process by altering the surface topography or chemical composition.

Final Surface: After treatment with phosphoric acid, the aluminum surface may be left with a different appearance or texture due to the formation of aluminum phosphate and removal of oxide layers. The aluminum phosphate itself typically remains adhered to the surface unless further processed or removed by subsequent treatments."

He goes on like that kind of repeating himself, as he has already done. The information provided is useful, so we can get the gist of what is happening to the surface. The acid reacts with the aluminum oxide layer you were talking about, removing it, and then leaves a layer of white crystalline stuff, (AlPO4) aluminum phosphate, on the surface. It is up to me to use the acid and, when finished, ask myself which surface look would I prefer, because it will be one or the other, I think. If I don't like the whitish look, scrape off the aluminum phosphate and let the surface return to aluminum oxide. These considerations are probably behind the missing clear (transparent) self-etching primer in the marketplace.

And, your first observation that considered all the manual interactions with the surface leaving what would perhaps be sufficient for the clear spray-paint to get a decent grip is probably a winner.

Very much like this comment you made, Thanks!

Lastly, to let you know that the paint company VHT has not yet responded. Maybe on Monday.

 

The phosphoric acid and paint arrived, but I have changed the plan and will come back to the acid and paint a little later than my original plan. And what my new plan will accomplish might make the acid cleaning actually be more effective, as the main aluminum parts will be more easily accessible. If I were a shop, I would have a bead blaster do that part, but I am not a shop.

Decided to do a minor overhaul of the W59 transmission before putting it back so I will have a good idea how it looks inside, and have a chance to clean it up and replace anything that looks damaged. Found an "overhaul kit" on-line that seems to suit, as it has three seals and maybe 5 gaskets, including the two gaskets that surround the intermediate plate and the front bearing retainer gasket. Anything extra in the kit would be for the other transmissions the product covers (i.e. W55, W58, etc).

Plan to remove the transmission case and its extension housing. examine the inside thoroughly, play around with the shift mechanisms a bit to get a better feel than the YouTube videos gave me, clean any gunk accumulated during the first 24 years of life, but don't expect to find much of that or any metal pieces laying around. Just want to know for certain what condition it is in.

Read through the FSM several times to make sure I will not saw off the limb I am standing on as soon as I crack it open. I have a question for you. The FSM says that the shift lever housing set bolt is a non-reusable part. That's the first time I have ever come across a (maybe 12 mm) hex head bolt that is not torque to yield but cannot be reused. Do you have any idea why they want that bolt to be new? It does lock down the shift lever housing that the shifter uses to execute each and every shift the truck will make going forward. It might be more obvious when I get to that point.

Another question: when you consider my new plan, is there anything you can think of that I ought to do either before starting, or at some point, to make sure I can put the thing back together exactly as it was before starting, say adding marks of any positions I need to return to, or anything similar. And do you think it will go back together as easily as I imagine? Anything I should watch out for? Anything you know that I don't could help me in the long run.

I'm still shopping for non-reusable gaskets and o-rings and the such that will be needed once it is apart, but after I place a couple more orders, it is coming apart.