About 5000 miles ago I had my original 3.73 gears put back into my jeep (long story) .Today I did a diff oil change and the oil was very black. The magnetic plug had about 1/8" to 1/4" of gunk on it. Does this indicate that the gears were put back in incorrectly or is this to be expected?

 

Gunk after only 5000 miles sounds unusual unless you went through some really wet mud that went into the breather and was churned into the oil with the action of the gears.

Another thought is maybe whoever installed them packed bearings and lubed everything with old fashioned axle grease, lots of it?

I would clean it out with some as well as I could and put some more oil into it, run it for another couple thousand and change it again.

 

Thanks, I had the dealership put my gears in and I think that was a big mistake. I'm getting 4.56s in a couple of weeks and I bought overhaul kits for it too so I imagine I should be good until then. This time I am going to get North Shore Offroad to intall my gears but they are on the mainland and I live on Vancouver Island. Sucks to take a ferry to the mainland for this but there is just knowone around here that does gears on a regular basis.

 

It is normal to have some metal filings/shaving on your diff plug as the diff has never been changed since installing the new gears.....your gears are just getting broken in....I had the same thing when I first changed mine.......Since you are getting lower gears installed shortly this will happen again.....I think you will always have a small amount filings on your plug each time you change your oil..... I would not be concerned, specially since the dealer changed it....if something happens, they should be covered on warranty...

 

when new gears are installed, it is sometimes crutial to go easy on them the first 5000 miles. no pedal to the metal hard speeding. this is because when they are installed the teeth do not mesh 100% and through the process of driving and lubricating and heating up to working temp the teeth mesh more uniformly