I just seperated the engine from the gearbox and wanted to clean the gearbox before replacing the seal and connecting it back to the engine. What do you suggest for cleaning off the 37 years of yuck? It's cold outside and I don't really want to be using the pressure washer, if that's a suggestion.

plastic scraper to remove thick chunks first
screw driver to gouge chunks out of corners
easy-off oven cleaner(name brand not generic) 30 min
EYE PROTECTION, GLOVES, scrubby brush and it comes off like butter
do not leave it on there more than an hour!!!
repeat proceedure if ya want it cleaner but do not leave oven cleaner on there more than 60 min (30 is best)

Dress warm, put on your rubber boots and pants. Then fire up the pressure washer. I would also try spraying on Castrol super cleaner. Be careful not to get any of the cleaner on bare skin.
Craig at CAMP

I used some generic oven cleaner and a pressure washer. Still looks like this 2 years later:

Click to view attachment

Many threads on this subject. Search for "tectyl".

Be careful with cleaners. Many can pit the mag case.

Eric, I think we might be related...

LOL... fitting.

Whatever cleaner you use, use it in a WELL VENTILATED area. If that means freezing tour little tootsies off, so be it. Especially that purple Castrol stuff. Better cold than in the hospital with breathing issues, possibly long term ones.

The Cap'n

Leaving the oven cleaner on too long is not an issue. It is not strong enough to do anything bad. I experimented with a case in my garage and left the cleaner on for a month. Re-wetted it occasionally, and nothing appreciable happened. So, 30min, one hour, not a biggie. Just be careful, ventilate, pressure wash where it can drain without staining your driveway (it will). With a pressure washer you have to be careful not to hit any of the seals or the vent directly. You WILL get water in the case no matter how you do it with a pressure washer, keep that in mind and change the oil afterward at least. I dont use a pressure washer, I use a hose. It is not as good on the outside, but it saves the insides from corrosion. If you can heat the case in a warm, dry area afterward that is also a good way to get some of the moisture out of the case.

Food for thought.

Tectyl is great for post cleaning coating. Whatever you do, especially if you are going at it with a pressure washer, only do that if you plan to pull the gear stack out, replace all of the seals, etc. The point is you don't want to force stuff into the case.

Also, in addition to removal of oil, grease, road tar and undercoating overspray, you will also find what I am seeing as two types of corrosion. The first is the pretty normal light grey you get from simple oxidation which is expected. I am also commonly finding something else that can be deeper/thick that causes pitting. It looks really different than the normal surface corrosion. I would love to talk to a chemist and/or metallurgist to understand what that is about. Anyhow, in my experience that has to be physically removed (i.e. bead blasting).

You may check with a local machine shop and tell them you have a magnesium case and see if they are setup to handle magnesium. Quiz them to ensure they know they can't use the same hot tank they would use for an iron block! Typically it would be via a water based parts washer that is like a big dish washer. If they can do it, they may be able to do it for you at a reasonable rate ($20 or so?)

Richard

the oven cleaner worked great but one time i left it on over night and teh case grew white fuzz. heat allways makes cleaning greasy grime easier.

Rich, the pitting that you are seeing is exfoliative corrosion. It is largely due to the salt we have here. It is pretty rare in non-rust belt states. When I was doing rebuilds in San Diego I dont recall seeing any with this. After moving to the East I see a majority with it. Generally, it is the tail cone that takes the brunt so I always have replacement ones on hand.

Once the mag is clean it will begin to form the white powdery oxidation. Mag is very easily oxidized. Read up on it in my 31 pages of notes. That is why after cleaning the case you need to coat it with something. The factory used Tectyl, but it only lasts about 1 year and needs to be reapplied. Spray paint would do a better job.

It may very well be exfoliative corrosion. And I wouldn't be surprised if it was related to salt. It is very odd in that you can have a transmission in which one area has little or no corrosion and another area nearby has significant amounts. It would be interesting to cut up one of those cases and look at the grain structure and see if those areas with pitting has a different structure than the areas that seem to survive. I have also seen one case in which it had a small localized corrosion in the differential cover and bottom of the case in which it had almost eaten a path from the inside out. The differential cover looked fine from the outside, but was not reusable. What will these cases look like in another 30 years.

Tectyl is good and my tests have shown it to last at least a year or slightly more (depending upon how you define at what point it needs to be reapplied). I also agree that some type of paint would be better than Tectyl, but the proper way to paint magnesium is an entirely different can of worms. You can easily find recommendations from the extreme of "rattle can is just fine" to "aerospace coatings/primers + special paints is the only way to go"

Richard

Great information

OK, think I'll try this on my case before it gets put back in to "222."

Which Tectyl does one use? There seems to be a hundred types.

Also any recommendation on how to put it on/how much to leave on would be greatly appreciated.

Also who carries this stuff?

Thanks.

Randal,

Let me look at my records and I can tell you where I bought mine and what type I bought. It's actually not expensive, but relatively difficult to find. What I use comes in a spray can. You put it on too thick and it just runs off. It is full of solvents, so give it a few days and it drys to a slightly tacky/waxy finish.

There are also some good threads over on Pelican about it. Pelican used to sell it, but I think it was a hassle due to shipping issues, so they quit selling it.

If you can't find Tectyl, I think a great alternative that is easier to find is "CRC Heavy Duty Corrosion Inhibitor"

http://www.crcindustries.com/marine/conten...=Y&PN=06026

It appears to be nearly identical to Tectyl.

Richard

Randal, it is Tectyl 846. Here is where I ordered it from...

http://www.mil-specproducts.com/productPage.aspx?prodID=446

I bought the spray cans. I can do about 3 transmissions with one can. For me the case works out cheaply for me, but in your case you might either buy the pint can, or just buy the CRC product I mention earlier as I know you can find it in single spray cans relatively easily.

Richard