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2006 chevy trailblazer_ss_3ss
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Discussion Starter #1
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. :hopeless

Let me know what you think.

Matt
 

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2006 chevy trailblazer_ss_3ss
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Discussion Starter #2 (Edited)
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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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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2006 chevy trailblazer_ss_3ss
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Discussion Starter #4
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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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:coffee
 

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2006 chevy trailblazer_ss_3ss
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Discussion Starter #6
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 :nono:

Good Luck Rick. :cool:
 

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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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2006 chevy trailblazer_ss_3ss
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Discussion Starter #8
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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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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2004 gmc
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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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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.
you just told us the problem...its the tune problem. what program are our using hptuner or efilive?
 

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2003 gmc envoy_slt_xl
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Grinding is always a baddddd thing ... however be careful with the dudes your talking to the Diff and the Actuator are not really related. Unless you have mega miles and chaos out of control - it should be one or the other. Why buy both?

Roadie has made some good points. If your Dif was run dry , big problem. If they drained it and the fluid was full of metal.....

If they did not drain it - you do it and see what you get..

But after my experience, the wheel bearings can make a lot of bad noises... start there.

Take it to a shop that will analyze it for free and let you sit underneath while they are doing it. Get them to set all wheels in motion up on the hoist and put one of those stethascope things on and see what kind of noises you are getting.

I had a real ugly noise that everybody pointed to Diff for, went to a couple places but one tech said to me start with the cheapest and work your way in. Wheel bearing, actuator , Diff.

Mine had 90,000 on it so I did both wheel bearings and regreased the actuator. Noise gone. I am pretty sure it was the drivers wheel bearing.
But did not have that sound - no side to side variation.

If you can get it on good stands - pulling everything but the diff is pretty easy.

Good Luck..
 

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2003 chevy trailblazer_ls_ext
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i believe the bearings on my drivers side front diff are worn. the cv axle going into it has alot of play.

can i change my diff from below while using jack stands in the garage ?

a mechanic on justanswers sais i have to remove the entire engine...i don't accept that solution easily.
 

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Roadie is The Man on these things and he says you need to lift the engine not pull it. Like he notes earlier if you can find the Haynes manual it must reference it.
 

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my driverside half axle move around in the differential....seems like a bearing problem.

QUESTION: can i replace the bearing without pulling the diff ? how can i determine if it is just the bearings, or if the entire diff should be replaced ?

CHALLENGE
i don't have a lift and use a floor jack. Can i do the diff without a lift ?

I guess this means disassembly of the hub and axle...i did this when replacing the shaft 1 year ago. it was a good job, but I didn't know i had to grease the bearings in the diff.

i might as well change the hub, too, since it is notorious to die at 100k anyway.

I'd be happy if the parts only include the bearings....that is $150-200 for the diff bearing kit...and $80 for each hub. sure beats $2k for parts and labor at the shop.
 

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2006 chevy trailblazer_ss_3ss
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Discussion Starter #17
you just told us the problem...its the tune problem. what program are our using hptuner or efilive?
I'm using HP Tuner.

Improper lubrication of splines is the primary fault. Secondary fault is a lack of thrust carrying capabilty in the tiny bearings in the bearing assembly.

Another problem...The beariing assembly part numbers for the AWD SS and for the 4x4 models have been discontinued...and there is no replacement part identified. I'm working through some GM engineering contacts to find out what's going on with these parts.
 

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2006 chevy trailblazer_ss_3ss
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Discussion Starter #18
my driverside half axle move around in the differential....seems like a bearing problem.

QUESTION: can i replace the bearing without pulling the diff ? how can i determine if it is just the bearings, or if the entire diff should be replaced ?

CHALLENGE
i don't have a lift and use a floor jack. Can i do the diff without a lift ?

I guess this means disassembly of the hub and axle...i did this when replacing the shaft 1 year ago. it was a good job, but I didn't know i had to grease the bearings in the diff.

i might as well change the hub, too, since it is notorious to die at 100k anyway.

I'd be happy if the parts only include the bearings....that is $150-200 for the diff bearing kit...and $80 for each hub. sure beats $2k for parts and labor at the shop.
I believe the right-side bearing is behide the side-to-side adjuster on the differential housing. I don't think it can be replaced without disturbing side-to-side ring position...and backlash.

The Haynes manual procedure is pretty involved...but doesn't require engine removal.
 

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Jackshaft Splines

I have had this same problem with my '02 Bravada. Mine had 150,000 miles when the AWD stopped working. I ended up replacing the jack-shaft and the coupling (The Bravada does not have a clutch - the front axle is always engaged) What I noticed was that all the grease that was in there was totally dried out. I imagine that having that bearing assembly mounted to the oil pan that the grease gets very hot. I completely cleaned out all the grease and re-packed everything with synthetic grease. I also noticed that the splines in the jackshaft are less than 1/2" long and all of the rest of the splines are well over 1" long.

I believe that the root of this problem (besided the inadequate spline length) is the AWD "software". If you have a limited amount of wheel slip the AWD engages gradually and it works really well and most of the time you never even know it is engaging. The flaw in their "software" is that in really slippery conditions the AWD engages really hard and you get a loud clunk when it engages. This happens all the time when I am pulling a snowmobile trailer and the driveway/road is slippery. I try to remember to accelerate lightly until the AWD is engaged before I really get on it. Sometime this is hard to do while manuvering in snow. I will never purchase a vehicle again that does not allow you to lock in 4wd all the time.

I wish I would have seen this posting before I fixed this problem. Thanks for all the good info tho.

Mike
 

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2006 chevy trailblazer_ss_3ss
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Discussion Starter #20
The spline engagement length for the bearing assembly interface is similar that of the opposite side of the shaft to the differential side gear. The failed side engagement length becomes decrease with the wearing of the thrust washers inside the bearing assembly. I'm including two other pictures, but I don't have a measurement picture for the side gear side to show the spline engagement witness mark length.

The trouble with my SS can't be relayed back to software. My center differential is a Torson T-3. It is completely mechanical and working all the time. The Stabilitrac system uses brake modulation and throttle control to vary the power at each wheel.

There is a lot wrong with the bearing assembly. I'm still waiting to here back from my contacts within Engineering at GM about the discontinuation of the bearing assemblies w/o a replacement number. I'm a Design Engineer for a major gas turbine engine design/manufacturing company. If I were given a "clean sheet" to design this bearing/intermediate shaft it would have thrust carrying capabiity within the bearings and differential oil for lubrication of the bearings and splines. If I could get rid of the splined interface, I would. For the AWD models, it could be done...the intermediate shaft would contain the splines that interface the CV drive axle splines. Since the intermediate shaft part number is currently common accross AWD and 4WD applications, I wouldn't be able to eliminate the splines on the AWD application. So, instead the spline engagement length would be increased to compensate for impact loading conditions.

The coupling/sleeve for the AWD bearing assembly has been on backorder for more than two months...and used parts are difficult to find. With the maturity of the 2006-2009 TBSS AWD vehicles, the sleeves will just become even more difficult to find. Lots of AWD TBSS owners are converting their vehicles to 2WD.
 

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