arzinet

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!

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. ? ? ?

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?!?

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

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.”

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?

Interesting conversation. I had a 2007 Suburban with the 5.3 that I bought new and was planning to drive forever. Filled it with synthetic from the first oil change (usually Pennzoil Platinum, but sometimes Mobil 1). I know they're not "real" synthetic, but close enough I figured. Followed the OCI as per the display, which resulted in oil changes every 8,000 to 13,000 km (5,000 - 8,000 miles.) I towed with it, in the mountains a lot, but tried not to abuse it. Changed all the other fluids regularly, never saw the coolant temp. gauge come up above normal, and only saw the tranny temps get a bit over 100 Celcius (212 Fahrenheit) on the longest climbs. I think 110 (230 F) was the highest I ever saw. Anyway, had the lifters fail at 70,000 km (43,000 miles), thankfully just after we got home from a long trip towing through the mountains. I'd heard of the issue beforehand, so it wasn't a total shock to me. The dealer was great, and everything fixed under warranty, so I wasn't too unhappy. The truck was fine for another few years and 50,000 km, then it got totalled in an accident. Replaced it with a 2011 Yukon XL 2500, and am kind of glad to have the old-school 6.0 now. Plan on keeping this one forever, as well. Still using synthetic, and still changing it according to the computer, but I'm starting to think maybe it wouldn't hurt to not go past 10,000 km between changes, regardless of what the computer says. Suppose I could get an oil analysis done, but I haven't yet. My other car is a VW, and it has its share of known issues as well. Worst one is a cam chain tensioner that is known to go bad, resulting in major engine damage (interference engine.) If you believe the internet, it will happen to every engine sooner or later, but of course there are no hard and fast numbers.