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Rear Diff Gears Are Black?


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So i finally got around to servicing my rear diff on my MJ and when i pulled the cover i found black gears, the whole inside was black. I sprayed break cleaner on it and wiped it with a red shop towel thinkin that'd clean it up.....NOPE....the whole inside stayed black, but the inside of the diff cover was black too and i got that to a nice bright shiny silver, any ideas why the inside of the diff is black?

 

The Diff Cover

The Top Of The Gears

The Bottom Of The Gears

The Head On View

Redwolf

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:agree:

If your concerned buy some less expensive gear lube....fill it up and drive a few hunderd miles....then drain and clean again....this time add high end gear lube.

 

Just out of curiosity since you had you diff cover off did you confirm your gear ratio? . :MJ 1: .

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I would guess its black because the oil was old or burned. The cover cleaned up because it is steel. The inside is iron and rough and holds all the junk. If everything looks good I would spray it out good and fill it up with new oil.

For some long portion of the trucks life, that gear oil was completely forgotten about.  Clean what you can and put in fresh oil.  It probably would not hurt to do it again within a few thousand miles too.

:agree:

If your concerned buy some less expensive gear lube....fill it up and drive a few hunderd miles....then drain and clean again....this time add high end gear lube.

 

Just out of curiosity since you had you diff cover off did you confirm your gear ratio? . :MJ 1: .

thanks guys, i was just wondering cause i've never seen black gears other than on my bosses truck but when we sprayed those, it came out silver (for the most part anyhow) but i think i'll do it again when i do my trans, unless is keeps leakin and i go the RTV gasket route; and yxmj, how'd i know ya would bring that up lol, no i didn't, i didn't have the MJ up in the air to spend the tires to count the teeth, nor did i have the time, i did this at work (since i get half off on everything and boss didn't care) and when i was finishing up it was an hour till closing,

 

Redwolf

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I would guess its black because the oil was old or burned. The cover cleaned up because it is steel. The inside is iron and rough and holds all the junk. If everything looks good I would spray it out good and fill it up with new oil.

For some long portion of the trucks life, that gear oil was completely forgotten about.  Clean what you can and put in fresh oil.  It probably would not hurt to do it again within a few thousand miles too.

:agree:

If your concerned buy some less expensive gear lube....fill it up and drive a few hunderd miles....then drain and clean again....this time add high end gear lube.

 

Just out of curiosity since you had you diff cover off did you confirm your gear ratio? . :MJ 1: .

thanks guys, i was just wondering cause i've never seen black gears other than on my bosses truck but when we sprayed those, it came out silver (for the most part anyhow) but i think i'll do it again when i do my trans, unless is keeps leakin and i go the RTV gasket route; and yxmj, how'd i know ya would bring that up lol, no i didn't, i didn't have the MJ up in the air to spend the tires to count the teeth, nor did i have the time, i did this at work (since i get half off on everything and boss didn't care) and when i was finishing up it was an hour till closing,

 

Redwolf

 

 

????? it is leaking??????do you have any type of gasket on the cover?

 

 And FYI if you had the cover off.....you would not need to "count the teeth" ,,,,,all you would need to do is read the numbers STAMPED IN THE RING GEAR.....

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 The inside is iron and rough and holds all the junk. If everything looks good I would spray it out good and fill it up with new oil.

 

 

all steel.  stamped, forged, cast or milled, it's all steel.  no cast iron. :thumbsup:

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