Rear differential vacuum or pressure?

Well,got paranoid and checked the wife's truck.2016 limitedDCSB4×4,NOT on the recall list no dark spots.Pulled the plug to see if they changed the fluid last time (15000miles),and there was a sound like either A:Vacuum,or B: Pressure?WTH?

 

Your rear end has gas.

 

Be careful of the back-pressure.

 

Great way to ruin your gasket...

 

It's fine and normal.

 

Differential oil like everything expands and contracts with heat and cold. There's a breather on top of the diff that is supposed to let gases vent out but I don't believe it is supposed to let air in. Could have been vacuum. Seeing as how your truck is so new, I doubt the diff breather is bad.

 

So the breather on top has a 1 way valve?Either way,the fluid was clean,not leaks,seeps or weeps.Actually, SHE made me do it since a guy at work told her to be careful with her rice burner, the rear end will lock up.3000000+miles under my belt,have had rear ends (differentials) leak multiple times.Not one has ever had a catastrophic failure. Axle seal,that's a different story.

 

Cannot say for sure on the 3rd gen, but breather valve on second gen is one way out. Check out the threads for breather diff mod.

I just changed the rear diff oil about a week ago on my 2015 and had the same sound as you. After changing the oil, I did the mod to allow it to vent both ways.

 

FYI, don't do the breather mod if you're on the recall list!

 

At 15k the OE fluid should be flawless. And if it's not, it's the bottom plug that will have sediment, not the top plug you check by for level.

Did they call it out on the service order? If not, it's the same ole same ole

 

Checked off that it was changed.Of course,I check stuff off all the time also.

 

@5K, when I changed mine, it was gunmetal colored paint. Was not clear or flawless. Had it been, I would have left it and topped off what leaked out. Was surprised actually.

 

I have under 14,000 on my 2015, but after seeing the oil others drained and the stuff collected on the magnet, I decided to drain and fill.
The drained oil was visibly darker than the replacement fluid and the magnet was covered. The factory fill might have still been good, but for the cost of a couple quarts Mobile 1, it was worth it to me.

Also replaced the transmission oil. Glad I did. Shifts much better now.