Cleaning Transmission and gears

[Ronald Sieber]

I'm going to post this query on the 912 Registry as well, but I thought that I'd start here, since we have some very skilled pros in transmissions on this site. And experienced hobbyists as well who have worked on trannies.

I have a 1968 912 5-speed transmission whose final gear was the "X" just like the 4-speed. I decided to have the 4th and 5th gears changed out for a "highway gear" setup. When my Porsche mechanic took it apart, he discovered this discoloration on all of the parts (see photos below). It had been stored dry, and it also was in my air-conditioned garage for two years as well before we opened it up. The parts do not seem to be rusty, and also they look dirty but do not feel so, which makes me wonder if they reacted to a cleaning agent.

I've attached photos to show what I am seeing. If you look at the tail pc cover and also the gear sets and plate, you can see a whitish residue on the aluminum, which appears to be a reaction to a base.

The bearings do not seem to have any grit in them. I'm puzzled. Does anyone have an idea of the discoloration? I do not think that it is rust - it looks more like a stain or residue.

Finally, I am going to re-clean everything and hope that this stuff comes off. Recommendations of solvents that will not react with aluminum? I know that gasoline cleans well, and I work in an open space, but there is that safety factor...

Thanks in advance - attached are some photos.

[Jon Bunin]

Ronald,

It has the appearance of a transmission involved in a fire, but I'm just looking at photos and cannot inspect it in person.

[WilliamVaughan]

It looks like it has had water in it. If it only had gear oil in it then it would not look like that.

[Al Zim]

I second the water in the transmission analysis. What is worse is that the water is inside the gears and probably deteriorated the bearing surface on the gears. Which makes repair expensive. al zim Vapor honing will not remove the pits from the rust.

[Michael Foster]

Might try vapor honing of gears and aluminum case. intermediate plate etc.

Michael Foster