Cleaning gearbox Options

[mgardstr]

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.

[Dr Evil]

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.

[Richard Casto]

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. (IMG:style_emoticons/default/huh.gif)

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