[Mark42]

Originally Posted by WildBillyT

.....Oh, and what "break in coating" is on the gears?

Originally Posted by Mark42

The dark grey coating on the gears is phosphorus. I was under the impression that it was there to assist with load break in. But I'm not exactly sure what the purpose of the phosphorus coating is. It could be just for corrosion protection. Whatever its function, I read in many places that the gear oil should be drained after the first 500 miles to remove any metal partickes and the phosphorus coating that will wear off.

So I know the grey stuff is phosphorus, just unsure what its function is.

I found this, and a few other websites that talk about phosphorus coating and maganese coatings that assist in break in process and reduce wear.

From sciencedirect.com:

The wear resistance of manganese phosphate coatings on steel and cast iron is reviewed. The effect of initial prephosphate chemical treatment on wear resistance was investigated. Treatment in baths based on manganese phosphate improves dry abrasion resistance which is independent of the type of initial chemical treatment. The best results were obtained after etching or etching combined with activation. Phosphate coatings effectively absorb lubricants. Wear resistance is more effective with lower quality lubricants. Phosphate coatings shorten the running-in period during normal service. Unit pressure, velocity of abrasion and the method of lubrication affect the wear process. It is concluded that phosphating enhances wear resistance when this is determined by loss of the base metal.

Bold added by me. Think this is what the coating is for?