Any tips/advice for cleaning the exterior of a transmission?

I scraped and got most of the obvious road dirt off it last night, but I'd love to paint this one after it gets back from Doc. Evil's GearBox Summer camp.

I am afraid to use a pressure washer for fear of water ingress, and obviously, the least amount of chemicals the better.

Thanks

I used engine brite and simple green... and a wire brush,

if I had a washer handy, I'd use that... it shouldn't get much water in it, and if it's going to be rebuilt anyway...

I used a wire wheel on a drill on the dry stuff, and lots of hours scraping the wet stuff.

put a cover on the vent hole.
Power wash it.

Rich

I think somebody said once to not use a steam cleaner on them, but I can't imagine why.
Steam cleaners work wonders and take all the hard work out of it.

I soaked mine in a degreaser I bought at Canadian Tire/Walmart rinsed it off and did the spots that needed it again and it came up pretty good. Don't forget to cover up the little vent hole. I think using a pressure washer or steamer is ok, just the back splash is real messy and sprays dirty oily greasy stuff everywhere!

Ian Stott
Moncton
Canada

Simple green and brush, that will do it.

Thanks, I'll do the simple green method first and if that doesn't do enough, I'll dfir up the ol' power washer, seal the vent and blow crap everywhere...

If you are going to wash it, a good idea is to take it to one of those go-it-yourself car washes. Dirt and gunk just washes away, and no clean up.

I use the oven cleaner that work out the best for me let it sit for 30 mins
then i pressure wash it came out nice and clean

DITTO the oven cleaner. It's made for cleaning baked on grease.
Simple green is made for cleaning dogshit off of the side of your shoe.

Wouldn't wheel cleaner like P21s wheel cleaner be good for cleaning transmissions. It's ph balanced and can get off caked on brake dust. It's $30 for a very small bottle though.

I hear griots is just p21s relabeled but for 1/5th the price. Haven't bought any yet but here very good things about it.


I would probably try this before I used overn cleaner. That stuff is pretty nasty.

Ok, So I didn't have any dog crap on my shoe so I went the oven cleaner route...

Well, it got most of the caked on grease off, and the tootbrush agitation helped some, and the power washer did the most of all, I think.

Looks like another 4 hrs of detailing and i'll have a pretty (clean, anyway) transmission.

SO, should I paint it?

Black?

I wouldn't paint it. Just creates more maintenance and holds more heat. Paint is for sealing metal to prevent rust, or for looks. The tranny isn't going to rust, and if someone does look under your car a clean tranny will look as good as a painted one. But then again, looks are subjective, so if YOU like the look of a color, go for it.

I agree with not painting it, if you have it all cleaned up as it sounds like you have ,it actually looks better that way. Periodic cleaning after that say when you change your oil or set your valves and it will always look good. Painting it seems to look funny and for me it makes me wonder what someone is trying to hide.

Ian Stott
Moncton
Canada

Ok, here we go again.

The trannys are magnesium and are treated with a protective chemical "pickle" coating.

When you oven clean it, the strongly basic solution eats the pickle.

Then the unprotected magnesium looks good for a short period of time until it starts to "rust". Mag rust is black and looks really ugly. Mag rust is accelerated by salt and moisture....

Since the protection is gone, I'd paint it. The zinc handbook (from my zinc parts design days) says zinc chromate can be used as a sacrificial coating. Unfortunately, the good grades of zinc chromate are usually aircraft grade and are bright yellow or green. Or, an epoxy or self etch primer is good. I used self etch primer and a thin silver color coat.

In any case, do a search. There are other options such as protective oils in other threads....

What? ME? trying to hide something?

I assure you that neither me, my lawyer, NOR my congressman(woman) are trying to hide anything... ever...

LOL, seriously, Thanks for the feedback.

I stand corrected! I will now check mine for corrosion and search out some of that paint and do mine. I don't drive in the rain or even if it looks like rain but have been caught, thankfully not too far from home.

Ian Stott
Moncton
Canada

I would use ppg dp90lf epoxy primer and leave it black but you could top coat it a color for more protection. Dp 90 is a nonsanding primer if you top coat it within about 12 hrs it has great adhesion between the case and the top coat paint. I would wait to paint it after it's rebuilt though.

I'm curious, why would you want to paint it? You DO realize that you're the owner of a vinyage car, right? So, why would you want to screw it's resale value by paint the tranny, which is nearly impossible to fully remove?

I don't get it! Why paint? Why not clean it up with chem's/steam & let it re-oxidize to its proper shade?

Apparently, I'm missing something here........

Cases are mag ALLOY not pure mag. I have used Easy-Off oven cleaner for years with no problems.

Cleaning mag and mag alloys is done by many industry folks using Stoddards cleaner, which seems to be a mineral spirit blend of some sort. The original cases were, and still are, pickled (acid) first and coated with Tectyl. I can find it on the worldwide websites but it's only available in the US through Daubert Chemical as Tectyl 553. I can't locate a supplier that will sell small amounts.

http://www.daubertchemical.com/main.taf?er...productLineId=1

Since the coating is supposed to not only reduce oxidation, but also seal the case, I thought that maybe CRC had something. They do, but it's equally hard to find. It's a spray-on aviation sealer / anti-corrosion stuff.

http://www.crcindustries.com/ei/content/pr...N=10200&S=Y

It's hard to find too. Darned frustrating since I'd like to seal these cases with the same technology the factory uses!

Both of these eventually wear off but can be reapplied. Anybody know a source for either one?

Well, looks like I should have waited about 2 more days before I acted...

I did the easyoff thing and now have no idea what to do.

It will be going to Dr, Evil on Friday, so I suppose i can do nothing for a while...

Thanks guys for all the information, always a wealth of it here.

I'm curious... Does someone have a photo of a 901 that was cleaned with oven cleaner some time back, and never retreated in any way with paint or sealant of any kind? How does it look now?

Ken raises a valid concern. Eric hears it after it's too late. Others indicate it's nothing to worry about. So, let's get to the bottom of this.

A coupla points:

First:- About mag corrosion from the internet....

"And while the corrosion rates of modern, high-grade magnesium alloys are acceptable for interior applications, the automotive exterior environments are extremely harsh for bare and even coated magnesium parts.

The interface between the steel bracket and a magnesium-alloy casting is prone to galvanic corrosion.
First, road salts and slurries can easily damage conventional electrocoat paints, creating sites for rapid electrochemical dissolution of magnesium. Second, being the most reactive (or anodic) metal in the electrochemical series, magnesium is prone to severe galvanic attack when in contact with other metals. In automotive structural components such as engine cradles, road salts and debris can accumulate around the bolts and washers that mechanically affix magnesium parts to the car frame. Such sites may become prone to galvanic corrosion (see Figure 2).

Therefore, finding cost-effective solutions for protecting magnesium alloys from corrosion has become paramount.

One of the best ways to combat galvanic corrosion of magnesium is to use isolation materials to prevent direct contact between bare magnesium and the dissimilar metal. If a high torque load is required, such isolation materials must be made of special metals or other inorganic substances that minimize excessive deformation upon loading. In particular, the use of aluminum washers can significantly reduce magnesium corrosion; however, the effectiveness of such corrosion protection is directly related to the chemical composition of the aluminum washer being used (see Figure 3). "

Now for protection:

My mag book suggested elements higher in the periodic table such as zinc to act as a sacrificial anode...

And according to the pelican 911 board....

The Factory Workshop Manual (Vol. I, page SR 140) sez:

“Warning:
Pressure cast parts must not be cleaned with acid, since acids attack the magnesium alloy. After any transmission repairs during which the one-season underseal is washed off the gearbox housing, or when the underneath of the vehicle is washed, we recommend that corrosion protection be improved on the pressure-cast gearbox housing by applying a bitumen or wax based one-season underseal, e. g. Tectyl, which should be sprayed or brushed on.”
© Dr. Ing. h.c. F. Porsche Workshop Manual, Vol. I, Page SR 140.


Tectyl in the wax formuation sounds a lot like cosmoline- the honey colored wax based wax protective coating that''s been around since at least WWII. A lot of european cars are shipped coated in "cosmoline" for protection and it's cleaned off with mineral spirits and a rag. If they didn't clean the tranny, that would explain the coating.

I'm sure there are other wax cosmoline or panel wax materials that look like the Tectyl....

Rust: No issue, this metal doesn't rust
Corrosion: Yes, it does. Detail the results: Darkish? Spread? We know it won't eat through the case, so it's a visual surface issue. Valid of course. Show us pics!

I wish I had pics of some of the shit boxes I have seen on the East Coast. There is definite exfoliating corrosion that goes on in the rust belt. I have seen tail cones that have no flat surfaces for the washers and nuts to seat against. When in CA, I NEVER saw anything like this. Salt, is the big contributor. Transmissions that I have received from FL from TC that have had sand and rust in side of them actually looked just fine on the outside. There is no way that the amounts of rust I have seen could be possible without the whole gear box being subjected to water over a very long period of time. There are pics of these gear boxes in their own threads as they were terrible enough to mention. The last one looked very clean on the outside, so much so that I was very surprised to find the insides completely rusted solid and rust flakes falling out of the case like sand.