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Originally Posted by alamantia
A couple questions because I am in the middle of a rear swap and in doing so desided to reread this post to find that you sited what I said and I have considered what you mentioned.
I see we agree on posi clutches and bearing requiring time to seat but what exactly is wear hardening? Is it a force that changes geometry after a part has been heat treated?
Also, if the gears have phosphorus lapping compound applied to them and gear lube is made from phosphorous how will the oil get contaminated?
I ask these questions because I am a degreed mechainical engineer whos first job was designing gear reducers. Ive never heard of either wear hardening or contamination of lube. I want to know if these are indeed factual because it got me thinking perhaps I should switch lubes in my cars.
I work in an industry now where we manufacture medical devices and have technical writing to support the usage and handeling of our products. Id say 10% of the writing is valuable and 90% is BS precautionary instructions that was only placed in the handbooks to serve as rebuttle if a product fails in the field and we were held liable we could use this literature in our defence saying the product want taken care of properly. This is why I find a lot of manufacturers suggestions a waist of time. I also was fortunate enough to grow up working in my fathers dealership. When rear ends came in that were broken or worn one of 3 things were done. It was under warrenty and the axle was taken out and a new one delivered. If it was out of warrenty the tech replaced either the bad gears or bearings or we got a used one delivered from hunts point. The very few times I have seen gear sets replaced the Techs followed GM proccedure and I dont recall them ever test driving cars for 10min clips or running them on jackstands or anything. They just drove them around the block, checked for leaks and called the customer to come pick up their cars and drive away. If someone has all-data and finds the gear installation proccedure and it calls for break in then I stand corrected. All-data proccedure reccomends every possible precaution, it tells you to remove the negitive batter cable for replacing spark plugs in some cases, im sure if break heat cycles are supposed to happen it would say. My owners manual in my car doesnt even suggest changing the rear fluid, just checking the level. So when people ask for gear break in advise. I offer my opinion and personal experiance. I personally find a lot of what manufactures suggest to be overkill and I hate to see people waist time and money on someting that isnt necessary. I like to think about why they suggest it and see if it makes sence and weigh that on what I know and decide for my self. But now you got me thinking.
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Work hardening is what the gear companies recommend because the gears are manufactured under different conditions that that which they run in. I posted a link above that Randy from Randy's Ring and Pinion wrote. And I can say with confidence that Richmond, Randy's, Motive, and Yukon Gear all say to break them in. I don't think jack stands would work as there would be little load being transferred and too little heat in the rear.
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Work hardening is similar to forging in the way that it compresses the metal molecules into a very compact and hard formation. This can only be accomplished if the metal surfaces are lubricated and the gear temperature stays cool enough that the molecular structure does not change. If the temperature of the metal gets hot enough to change the molecular structure, it will soften the surface instead of hardening it.
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