redwolf624 Posted May 13, 2014 Share Posted May 13, 2014 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 Link to comment Share on other sites More sharing options...
nitroxsteve Posted May 13, 2014 Share Posted May 13, 2014 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. Link to comment Share on other sites More sharing options...
Timeless Posted May 13, 2014 Share Posted May 13, 2014 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. Link to comment Share on other sites More sharing options...
yxmj Posted May 13, 2014 Share Posted May 13, 2014 :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: . Link to comment Share on other sites More sharing options...
redwolf624 Posted May 14, 2014 Author Share Posted May 14, 2014 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 Link to comment Share on other sites More sharing options...
yxmj Posted May 14, 2014 Share Posted May 14, 2014 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..... Link to comment Share on other sites More sharing options...
Pete M Posted May 14, 2014 Share Posted May 14, 2014 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: Link to comment Share on other sites More sharing options...
dasbulliwagen Posted May 15, 2014 Share Posted May 15, 2014 Of all the diffs Ive serviced, yours looks completely normal to me, I wouldnt worry about it, especially if its still quiet while driving. Refill it with good fluid and enjoy the drive! Link to comment Share on other sites More sharing options...
nitroxsteve Posted May 15, 2014 Share Posted May 15, 2014 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: True, Link to comment Share on other sites More sharing options...
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