Front Differential Failure - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2006 - 2009 TrailBlazer SS Tech > 06-09 SS Engine and Drivetrain > AWD Drivetrain

AWD Drivetrain AWD repairs & problems

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  #1  
Old 07-21-2009, 11:12 PM
MKETBSS79 MKETBSS79 is offline
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2006 Chevy TrailBlazer SS (3SS)
Black 6.0L LS2 V8 AWD
Join Date: Jul 2009
Location: Indiana
Posts: 17
Front Differential Failure

Hello. I just joined the forum to search for issues within the front drive axle assembly. My initial searches tell me that the front diff is pretty stout...so I shouldn't have broken it.

I accelerated away from a dead stop, went through a wide-open-throttle 1-2shift, and heard a loud pop followed by a grinding sound. The vehicle no longer move under its own power. I took a closer look after flat-bedding the truck home. I have input from my front driveshaft into my front differential, but I have no outputs. I'll be tearing it apart in the near future...so I'll post the carnage pixs when they become available.

Like I said at the top, the front diff doesn't seem to have a reputation for instantaneous failures. My setup is harder on the geartrain that stock...but just through the use of higher shift pressures, quickened shift times, and omission of most of the torqur reduction during shifts. My tires (275/45R20) and a mild exhaust mods are the only mechanical changes to the truck. I've also added a little fuel and timing to my tune, but not much. No power adders...stock shift points.

I'm hoping this is just an odd-ball problem...Anyone else having this kind of problem? If so, is there a stronger (larger) front diff assembly that is a bolt-in option? I'm guessing there isn't because the passenger side intermediate shaft that passes through the oil pan. If there is a bolt-in, I bet would require a new oil pan too.

Let me know what you think.

Matt
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  #2  
Old 07-26-2009, 08:56 AM
MKETBSS79 MKETBSS79 is offline
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2006 Chevy TrailBlazer SS (3SS)
Black 6.0L LS2 V8 AWD
Join Date: Jul 2009
Location: Indiana
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I had a chance to teardown portions of the front drivetrain. The failure was not the differential itself, but instead the splined connection between the jackshaft and the bearing housing on the passenger side of the oil pan. The splines on the jackshaft have stripped out. I'm going to need to replace the jackshaft and the bearing housing.

I'm not certain what the actual failure mode was. Take a look at the pictures...the splines are completely lacking lubricant, so they have been wearing at an accelerated rate. Maybe that reduced the tooth width and made it easier to strip them out. I don't think these splines should be dry...but the don't get oil from the diff side. I'm going to have to fix that issue too.

Has anyone else had this failure?
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2006 Trailblazer SS AWD - Tuned: 13.81 @ 99.5 mph
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  #3  
Old 07-26-2009, 09:36 AM
johnm johnm is offline
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2002 Chevy TrailBlazer LTZ
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This is the same problem I had, plus the outside bearing was destroyed. An expensive fix if you go with new parts. I was able to find one at the salvage yard for $250. There is no way to check or lubricate this case. I suggest that every 20,000-40,000 pull the half shaft and add some GP4 grease.
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  #4  
Old 07-26-2009, 09:43 AM
MKETBSS79 MKETBSS79 is offline
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2006 Chevy TrailBlazer SS (3SS)
Black 6.0L LS2 V8 AWD
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I was just relieved that I didn't blow up the front differential.

There is a grease point on the bearing housing, but it looks like it would only be able to get lube to the bearings, not the splines. Thanks for the reply...I'll be pulling the shaft every so often. That will be a lot less painful than finding and buying these parts a second time.
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  #5  
Old 08-14-2009, 06:08 PM
playstrings playstrings is offline
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2003 GMC Envoy SLT XL
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Hi Guys,
I have an envoy 5.3 with a buzzing up in the diff.
I am working on my garage floor and my head is getting harder as this thing ages. - How hard is it to get that spline out and look at things?

The dealer guys were a bunch of bozos - change the fluid and see if it helps. Right meantime something is rubbing bad.

started as a low low buzz but has graduated to a steady brrr. Next step is a grind LOL....

Thanks for your help.
Rick
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  #6  
Old 08-19-2009, 12:53 AM
MKETBSS79 MKETBSS79 is offline
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2006 Chevy TrailBlazer SS (3SS)
Black 6.0L LS2 V8 AWD
Join Date: Jul 2009
Location: Indiana
Posts: 17
Not a fun job...but most of those kind of jobs aren't.

There are some differences between the 4WD and AWD versions. Your truck will have a shift fork and an electric motor...so there may be some additional work to remove the bearing housing from the oil pan. Also, you may be hearing something not fully engage within that splined connection.

The good news is that the bearing assembly doesn't need to be removed from the oil pan to determine if the splines are dry. You just need to get the cv drive axle out of the way. That procedure is essentially the same as most front wheel drive vehicles. I removed the brakes, upper two bolts for the shock/spring assembly, outer tie rod end, upper ball joint, and lower ball joint...in that order. Then a quick slap on the inner tripod of the cv drive axle gets you to the splines. The picture below shows what you'll see at that step. In my case, I could see that the splines between the intermediate shaft and the bearing assembly were no longer engaged with one another. To get a good look at all the splines, the bearing assembly needs to be removed. To remove the bearing assembly, the transmission cooler lines had to be unclipped and moved aside. After removing the bolts, the AWD bearing assembly comes right off. Like I mentioned earlier, there may be some additional steps associated with the remove of the 4WD bearing assembly.

By the way...there is no fluid in that bearing housing, just grease. They (the designers) should have used differential fluid because those splines are "flexible" or "working" involute splines. That type of spline needs to be cooled and flushed free of debris by fluid...the grease doesn't get it done and doesn't handle the pressure. Bad design choice for spline lubrication

Good Luck Rick.
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  #7  
Old 08-19-2009, 09:14 AM
playstrings playstrings is offline
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2003 GMC Envoy SLT XL
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Holly Cow !! That mess is on your 2006 SS ?? How many miles when you took it apart ?

Thanks for the notes... today is the day LOL...
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  #8  
Old 08-19-2009, 11:44 PM
MKETBSS79 MKETBSS79 is offline
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2006 Chevy TrailBlazer SS (3SS)
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Location: Indiana
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No problem.

My mileage was only 62k. But that is the wear with full time all wheel drive...a part time four wheel drive application would take longer to accumulate that kind of wear.
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  #9  
Old 09-01-2009, 11:40 AM
luv2av8 luv2av8 is offline
 
Join Date: Sep 2009
Posts: 2
2003 Acsender with differential noise (grinding)

The pics posted referencing the front differential and the associated bearings and splined shafts is quite helpful. I am having an issue with the front differential. I was told (after a transmission shop spun the drivers side wheel and heard the noise I told them about) that I need to replace the whole differential as well as the passenger side actuator assembly (the part that the cv connects to once the shaft is through the oil pan (what a strange bit of engineering) and then to the cv shaft to the wheel). The cost for the parts is quite hefty. Has anyone out there had the same issue and found that the problem was easily fixed with a few hundred dollars worth of parts and several hours of labor to rebuild rather than replace with used. I am being told that it is going to take about 8 hours to rip out and replace the front diff and about a grand in parts. Are these guys telling me the truth or taking me for a ride?
I am a pretty fair mechanic (having replaced motors (350ci) in boats as well as rebuilding on the bench) but looking up at where this thing is looks like it is not the job for a weekend mechanic. I can't imagine how you would get the differential out of there. Any ideas?
Thanks
BTW any ideas how much a used front differential should cost?
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  #10  
Old 09-01-2009, 11:51 AM
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the roadie the roadie is offline
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The driver's side wheel is ALWAYS connected to the diff, so if it made noises, it's got real problems. How many miles, and were you checking the fluid level as often as the Owner's Manual said? Just to make sure you don't lose the transfer case, did you change its fluid at 50K?

You have to raise the engine with a lift to get room to swap the diff. A Haynes manual might be a good investment.

Diffs go for as little as $500 on Ebay or www.car-parts.com, the junkyard data base where you can sort by distance or price.



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