I changed the transfer case fluid in my 2017 Cadillac Escalade at 51,000 miles. Lots of metal filings, very dark liquid. Replaced with GM OE gear oil. Saved a lot of money by not going to the dealer. The owner's manual says to change the fluid at 97,500 miles, but I'm glad I saw the "That Shorty" video on YouTube, specifically the 50,000 service for the 2015-2020 Escalade.