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2011 Yukon XL 2500 front diff pinion seal leak

arzinet

By arzinet
in Ask A GM Technician

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arzinet Enthusiast

arzinet

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I bought this truck in 2012 with 20,000 km on it. It's now at 170,000 km and over that time I've had the front diff pinion seal replaced four times due to leaks. I've even had the front diff removed, rebuilt and resealed, and still had the pinion seal leak again a year later. I took it back and they were nice enough to replace the seal for me, but now it's six months later and leaking again.

 

Mostly the earlier leaks were just slow drips, but this time it sprayed oil all over the exhaust, making a hell of a smoke show. Wife had to pull over on the highway and a passing motorist ran over with a fire extinguisher, thinking it was on fire. Not a fun time.

 

Is this just an issue with these trucks and it's always going to leak? I asked the shop the last time to triple check everything to make sure there was no other issue that could be causing the seals to leak so quickly, but they assured me everything was fine. They just said maybe it was a bit of dirt or something under the seal and "It happens sometimes." Yeah, but four times in 150,000 km?

 

And it wasn't just one shop - I've had the seals replaced at the dealer as well. Time to find a third shop who knows what they're doing? Anything I should ask them to look out for?

 

 

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Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Where is the seal leaking, is it between the seal and the housing, or between the seal and the pinion?  Its not leaking by the splines of the pinion gear and the flange is it?

If it is between the housing and the seal, generally RTV around the seal will stop it.  If it is between the pinion flange and the seal, it may be time to measure the diameter of the seal area on the pinion flange and compare it to a new one.  If its between the splines and the pinion flange, again RTV is your friend.  Trick to RTV is to let it cure before exposing it to oil.  Oil will just wash it away.  If you can get the shop to do it on a Friday afternoon and then let it sit till Monday before refilling the housing.

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arzinet Enthusiast

arzinet

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Thanks, I’ll have to clean it up and take a closer look. Right now the whole area is covered in gear oil, so hard to see exactly where it was leaking from.

 

It sure seems like it was being flung all over the place, so I’m guessing it was leaking between the seal and the pinion? My wife had it in Auto AWD when the smoke show happened, so the shaft would have been rotating. I’ve told her to keep it in 2WD and it’s been okay since.

 

And I never paid too much attention before, either. Mostly I’d notice a few tiny drips on the driveway, then I’d take it in for an oil change or other service and the dealer would say “Oh, the front diff pinion seal is leaking too.” 

  • 5 months later...
arzinet Enthusiast

arzinet

Posted
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Well, thought I'd update this - mostly just to vent. :fume:

 

So I took the truck to another shop in the fall. Aside from the leaky pinion seal, it turned out that the pinion bearing was shot as well, so I spent $2500 to get the front diff rebuilt (again!) This is a recommended and respected shop, specializing in drivetrain only. They sent out the diff to their remanufacturing facility for a complete overhaul, and apparently came back as good as new.

 

Fast forward to today, four months later, and I step out of the truck to be greeted by the unmistakable smell of burning gear oil. Took a look under the truck, and of course the pinion seal area and everything behind it is covered in oil. :fume:

 

Okay, so that's pinion seal number 5! What the heck is going on here? I'm taking it back to the shop on Tuesday, but would like to come up with some ideas in the meantime. All I can think of is that there's some kind of casting issue with the case itself that causes the pinion seal and/or bearing to not seat properly. But supposedly they measured and checked out the housing before rebuilding it, and said everything was fine.

 

Or what about an off-balance front drive shaft? Maybe it's shaking enough to mess up the seal and eventually the bearing? Seems plausible, but I can't say I've noticed any unusual vibrations when driving in 4WD or AWD.

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silveradosid Senior Enthusiast

silveradosid

Posted
Posted

two things come to mind one is has any one checked to see if the vent is plugged and two is did the rebuild shop put a new yoke in. alot of rebuilders like to use what is called a ready sleeve on old yokes. it is a sleeve that is pressed on the old yoke to give the seal a smooth surface to ride on. because the sleeve is a larger diameter it stretches the seal or cuts the edge of the seal and always end up leaking. i own a transport company and have had this problem with the rebuilder i have been using for 30 years. i dont care of the cost they now know to put a new yoke on

arzinet Enthusiast

arzinet

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Posted (edited)

Thanks, I'll definitely ask them about that.

 

I've read about the vent being plugged. That seems like a common enough thing that I'd sure hope any decent shop would check that first and make sure it's clean. Especially if they've already pulled the diff and it's all apart sitting on the bench. Guess you never know, though.

 

Nobody mentioned the yoke sleeve, either, but I'll ask about that too.

 

The odd thing is that the pinion seal has been leaking since the truck was new - I had it replaced twice under warranty, so it's been an issue long before either of the rebuilds. Something else has to be going on here?!?

Edited by arzinet
  • 6 months later...
arzinet Enthusiast

arzinet

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All right then, what the hell, time for another installment in this saga!

 

So, took it back to the shop in February. They apologized for the leak, replaced the pinion seal again (for  the sixth time!) and installed a new yoke for free (just to be sure, they said.)

 

Haven't smelled any burning gear oil since then, so thought all was good. But, of course not... Just got the truck back from an oil change at the dealership and just about lost my mind when I saw this in the comments: "Multiple leaks at front differential: Shift fork motor seal, LH/RH output seals."

 

At least it wasn't the pinion seal leaking again this time. ? ? ?

 

 

  • 2 years later...
Doug Teeple New Member

Doug Teeple

Posted
Posted

I have a 2013 sierra Denali it started doing the same thing in 2020 i am now stranded 500 miles from home on the 4th pinion seal in 3 years. Last July I was stranded in Southern Indiana  they said it was a kinked breather hose they rerouted but here iam again stranded in less than a year. It's at the local gm dealer  waiting for Friday to see what's up. Been talking to GM about the whole story and how we are lucky it didn't lock up while pulling a 30ft travel trailer. We will see what this Certified GM mechanic says. 

  • Sad 1
swathdiver Senior Enthusiast

swathdiver

Posted
Posted

Sorry about your luck fellas.  After the 3rd one I would have replaced the unit or rebuilt it myself.

  • 3 months later...
arzinet Enthusiast

arzinet

Posted
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Just to wrap this up...

 

All along it was just a plugged breather hose. Can't believe it was such a simple thing, and also can't believe that nobody thought to check. It was plugged up completely solid, but the last shop managed to blow it out and it's been fine ever since. Going on a couple of years now with no leak!

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