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Username Post: Changing rear diff lube        (Topic#368673)
Frequent Contributor
Posts: 1340

Loc: Tennessee
Reg: 12-06-10
06-12-22 04:14 PM - Post#2842785    

Changed the gear oil in the rear diff of a 2015 Yukon Denali. Cover bolts (screws) were so hard to turn I was afraid of twisting them off. Tried three different ones and all took over 40 ft/lb to move them and continued to require a lot of torque to turn them, they did not get looser. So, I turned them back to about where they were and left them alone for fear of breaking them off.

Ended up sucking the oil out and refilling it with the cover on. Anyone else experience this issue with 2015-2020 Yukons, Tahoes, Sierras or Silverados differential cover bolts?

Frequent Contributor
Posts: 1411

Loc: Orlando Florida
Reg: 07-09-18
06-12-22 04:43 PM - Post#2842794    
    In response to YOUNG57

The vehicle may have been in a corrosive climate is all I can say.

Unless someone has had it apart before and used thread locker on those bolts, I have no idea.

People fear change because it threatens what they know, or what they claim to know.

Frequent Contributor
Posts: 1340

Loc: Tennessee
Reg: 12-06-10
06-13-22 06:21 AM - Post#2842820    
    In response to Tony1963

It hasn't been in a corrosive environment, very little sign of rust any where. The gear oil I took out was very black so I feel it may have been original. But thread locker was my guess too.
Thanks for responding.

Dedicated Member
Posts: 5553
Loc: Lake Superior-Michigan US...
Reg: 03-30-00
06-16-22 03:47 AM - Post#2842966    
    In response to YOUNG57

Did you try squirting some penetrating oil on the bolts? They still could be rusty. I doubt they waste money on thread locker when the build these.

Black or dark brownish typically means its oxidized. Keep in mind, if oem then it was put in at the axle plant and you can bet they source the lowest cost gear lube.

2021 GMC 4WD Sierra Denali CC 6.2L/10-sp
2018 Polaris RZR S 900 EPS
2017 John Deere X738 Snow Blower

Frequent Contributor
Posts: 1340

Loc: Tennessee
Reg: 12-06-10
06-20-22 12:41 PM - Post#2843149    
    In response to elcamino

This weekend I changed the rear differential gear oil in another 2015-2020 Yukon (my 2019) and decided to try a little harder to remove this cover’s bolts. Used a 12” long 3/8” drive breaker bar. Much smoother than with a 3/8” drive ratchet, they didn’t feel like they were going to break (twist off).

Turned hard all the way out. Turns out they were all coated with thread locker, no wonder.
Changed the front diff oil and transfer case fluid too and glad I did. Original front and rear diff oils were black and transfer case fluid was dark orange at only 38,000 miles.

I decided to put in a drain plug in rear diff, like the front diff and transfer case, so I wouldn’t have to remove the cover each time. Drilled and tapped for an 1/8” pipe plug next to the magnet and wa la, next time it will be a breeze.

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