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I happened to look under the rear of my 2020 STX 6.2L CCSB today and noticed the stain on the diff cover. Its a 3.73 Electronic Locking diff. Has anyone had a similar stain and did it turn out to be a problem? Mine is due for a service visit so I'll get them to determine what is going on. Thanks
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As long as it's not coming from the pinion, it's only as big of a deal as you make it. Based on your picture from the rear, that is just a little weeping from the cover seal.
OP, is it just on the rear cover, or is it damp around the pinion and then blowing back from thw wind at speed?
If it is just the rear cover, you might try a wrench on the bolts and see if they are all tight, if it actually the pinion seal, that’s what warranty is for.
At the least, keep an eye on it. It's kinda young to start leaking. If it drains, the differential will seize while you're driving. It has happened but usually on older trucks where the cover rusted through.
It could be oil from the engine or tranny. It's weird but oil does fly backwards and can end up where you're seeing it. It's also possible someone was sloppy filling or checking the oil. Either way, it needs to be figured out. It really sucks when they leak themselves dry.
