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Discussion Starter · #1 · (Edited)
Rebuilt a 300 rear diff.

Used Caltric gears (pressed not welded) which are supposedly good. Used Boss bearings. Shimmed the ring gear.

Sold it to a guy and he ran it for a day, and when he changed fluid it had some flakes in the oil.

Obviously he's concerned. Is this normal with new gears? I know on a lot of vehicles it is with brand new gears. I've done bearings in a few diffs, but reused the ring and pinion so this is my first "new gear" rebuild. I did get the ring gear properly shimmed. I'm familiar with gear setup.

I told the guy to run it for a week, drain it and see what he gets.

If he's not happy I'll refund him or send him a 250A rear I have as a spare, but for those who have rebuilt a lot of these, are some small flakes unusual on break-in?

My only firsthand experience that says "normal" is a new Toyota rear end will leave flakes on break in (saw that on a Taco rear) After break in oil change they go away.

Any input?
 

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no , never seen any of my rear end oils look like that , but I only done a few new after market 300 gear sets before going to the 250 rear ends , and they had so much mud in the oil that you couldn't have seen the flakes if they were there . LOL ----but that don't look good , very shiny , wonder if it is aluminum housing and not metal gear teeth , a magnet might tell
 

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^^^^^ Agreed I'd try a magnet to see what type of filings those are
 

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I've set up a gazillion of them in cars and trucks. Some of them will shed for a while and some never do. I think it depends on how well the gear pairs were matched at the factory (and if they were lapped in as a matched set or not) and whether the tooling was fresh and sharp, or not. You set them up right and they aren't noisy, so I'd run them some more until they get lapped in. If you still see heavy shedding after 10-15 hours of runtime, then you might have gotten a bad set of gears (it happens a lot, no matter the brand)... and they'd have been getting quite noisy by then. If its a bearing issue it'll get worse, very fast...
 
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