CREWCABDAD

So I decided to change out the fluid in my front and rear differentials. The rear went fine with the fluid appearing completely normal. Even has a reusable gasket. The front however was a different story. I was going to put it off another week but when i looked in the fill hole the fluid appeared bubbly. It was just below the fill hole. So i drained it out and it came out grey in color, foamy, and with a consistency similar to a thin pancake mix. The truck has 15000 miles on it and I bought it new. I probably have less than 500 miles with the 4wd engaged. This check was done with the truck cold and the 4wd had not recently been engaged. I am by no means a mechanic but i have changed gear oil in several of my vehicles, tractors, and 4 wheeler. I have not seen fluid like this. I am glad I decided to look. Has anyone seen anything like this? Any recommendations? Seems very odd for such low mileage and usage. I have never submerged it and the breather is intact. I attached some pics.

Cowpie

Wow. That is strange. That fluid looks highly oxidized. My recommend is since you changed it, you do so again in 500 miles and see the results. It is conceivable the wrong fluid was put in initially. You have reaffirmed my methodology to change out factory drive train fluids in the first 5000 miles. You will probably get some of this again at the 500 mile change, but do it again and change again at 500 miles. That should clean things out. Then watch closely from then on out. At least in the next 2000 miles you should be able to see if this will repeat itself and get it into a dealer to check out.

CREWCABDAD

I agree with your thinking. My last 2 new trucks had everything swapped out by 5000 miles. For some reason with this one I put it off. I figured I'd wait a year for the axle fluid. Hasn't even been a year. Too long though I guess. Imagine if I trusted the manual. It states that it is not necessary to check the fluid unless a leak is suspected. The guy at autozone looked at me like I was crazy for changing the fluid so soon. Everything I have read coincides with your 5000 mile rule. But there is no good reason for the front fluid to be in that condition. I do not have any problems with the 4wd, but I saved samples of the fluid just in case I do. The gears looked ok from what I could see but I worry about the longevity of the bearings. That stuff looked no god coming out.

Duug4

Okay, can you provide any possible causes of this at that low mileage? How have you determined it is not normal? What other 2015/2016 Silverado front axle fluid do you have experience with? Did you show your sample of the fluid to a GM truck mechanic for an opinion?

tech2

grey fluid is caused by moisture in the fluid. if you have not been fording any streams, its from condensation. do you live in a cold area or have large diurnal temp changes? change the fluid and you will be fine. Its not uncommon. make sure the vent can pass air and is in place.

why the front and not the back...maybe the front runs cooler when in 2wd?

use a full synthetic fluid

CREWCABDAD

Thanks for the responses. I have owned 7 4wd gm vehicles with various mileage and changed the front and rear fluid on six of them. I have just simply never seen fluid come out like this. I assumed it was moisture but couldn't figure out how I could have gotten enough moisture in it to affect it like that. But yes, I do live in ny where the climate changes frequently. I go through the winter where I engage the 4wd frequently to spring, summer and fall with minimal to no use. So condensation does make sense. I just haven't seen it like that before. I was just hoping that someone with more experience than me may have seen this before. There is no noticeable damage to the differential and it functions as it should. I can't take it to the dealer cause there's not actually a problem and if they had done the work i would have never known about the fluid. I did check the breather and it is intact. I plan on changing the fluid again as suggested. Like I said, I just wanted to know if anyone had seen this before and whether or not they had problems afterward.

TonkaTruck

Wow; I'm worried now as my 2014 truck is getting close to basic warranty expire. I had a front left wheel bearing replaced under warranty very soon after getting the truck, due to grinding noise. I suspect it was probably not properly lubed, if at all.

tech2

the most likely cause is a broken vent tube allowing the water to enter the diff. is the filter cap in place on the vent tube?

Brian Thompson

tech2

yep, keep an eye on it. If you hear any howling or whine noises get it to the dealer before you warranty runs out.
the metal shavings were only on the plug magnet or throughout the fluid? any pics?