Question for the AWD van guys - issues with your front differential/carrier?

[zuren]

I wanted to throw this out to the AWD Express and Astro/Safari guys on the board to see if I'm in the minority.

Has anyone with an AWD front differential/carrier (GM 7.2" IFS used in the Express and Astro/Safari vans) had issues yet with carrier bearings? I've been chasing front-end drivetrain noises and "think" that is what I have now found. I grab the driver-side CV axle and get about 1/16" of play in all directions from the flange that comes out of the side of the differential. I'm not experienced with these systems but I'm guessing that isn't normal. A mechanic buddy of mine said there should be no play at all so I took a video of me manipulating it and sent it to him to see what he thinks.

I've done a bit of searching online and it seems that the AWD GM truck guys describe exactly what I'm seeing and hearing and it is relatively common. The front differential for AWD is engaged all of the time and they chew up carrier bearings, typically the driver-side, to give you play and bearing noise. I drained the fluid, ran a magnet through it and have a magnetic probe I slid into the drain hole - no STEEL chunks found anywhere. I'm not sure what kind of a repair I may be in for. I can't know for sure but I believe everything is factory with 128k miles on it.

Thanks!

EDIT: Went back and checked the fluid again. It was loaded with aluminum shavings! The stuff is so fine I could hardly see it. It looks like an extremely fine aluminum dust was dumped into the diff.

 

[ihatemybike]

I haven't had any issues with carrier bearings yet, just worn out axle seals. What does the noise sound like?

 

[zuren]

I haven't had any issues with carrier bearings yet, just worn out axle seals. What does the noise sound like?

Please disregard the intro (Booster is my buddy's nickname):

http://s4.photobucket.com/albums/y139/zuren1cs/Van/?action=view&current=MVI_1797.mp4

You can clearly see the play in that clip that I don't know if it is normal. The noise when rolling on the road is a "whirring" sound directly under my feet.....sounds like bearings with sand in them that starts at ~20 MPH and gets louder as speed increases. I've read that a bad carrier bearing should sound like a rumble; I'm wondering if I'm catching this early in the process.

 

[nely]

Is it only on the drivers side? Sounds like the unit wheel bearing going out

 

[zuren]

Is it only on the drivers side? Sounds like the unit wheel bearing going out

The driver-side wheel bearing assembly is still a possibility especially since I replaced the passenger-side earlier this year. It sounds like it is under the driver's feet. The problem with the wheel bearing theory is that the noise is constant; doing the "left-hand turn, right-hand turn" test doesn't change anything. The other problem is when driving next to a concrete barrier or in a tunnel, I cannot hear the noise being reflected back at the vehicle. It's been my experience that when a wheel bearing goes, you can hear it outside of the car if you're next to something that can reflect it back.

The wheel bearing was my #1 possibility but before I ran off to spend $180 and a day messing with it (it was a pain to get the other one off!) I crawled underneath to find that flange able to wobble. That gave me reason to pause and do more research.

 

[ihatemybike]

That's more play than I've seen in my vans. I'd want to pull the shaft out and inspect the splines before I go after the bearing. I've seen similar wiggle with my wife's Jeep due to bad splines.

 

[zuren]

I wanted to update this thread:

I went back and checked the fluid to find extremely fine aluminum shavings suspended in the oil. I couldn't see it before. It took me putting the fluid back in using a clear Tygon tube to see little shiny flecks passing through. It certainly appears that there is an issue wearing at parts of the outer case.

 

[wookee]

Anyone have any idea what a front rebuild is going to cost? My diff is screaming and I'm kinda wondering what kind of bill I'll eventually get from the mechanic. It's a 2005 express awd.

 

[zuren]

Anyone have any idea what a front rebuild is going to cost? My diff is screaming and I'm kinda wondering what kind of bill I'll eventually get from the mechanic. It's a 2005 express awd.

wookee - Have you narrowed it down to the diff.? It could be the u-joint.

Depending on what is going on, a rebuild may not be possible. Have you checked the fluid? If it's loaded with very fine aluminum shavings, one of the bearings may be machining out the case. You would need a new case and at that point, I'm told that it's easier to just get a different one.

I'm looking at used units for $650, rebuilt units for $950 and new would cost $1500.

 

[wookee]

My understanding right now is that it's the inner bearing on the driver's side of the front diff. That's all I know for now, but I'll update as I hear more during the week.

It's a 2005 and I just got it for $2400, so I expect another $1500-2k in problems I'm going to have to sort out. Lucky that it's in good enough shape to justify fixing it.

 

[zuren]

My understanding right now is that it's the inner bearing on the driver's side of the front diff. That's all I know for now, but I'll update as I hear more during the week.

It's a 2005 and I just got it for $2400, so I expect another $1500-2k in problems I'm going to have to sort out. Lucky that it's in good enough shape to justify fixing it.

That is the bearing that typically goes bad. I would check your diff. fluid and look closely for fine aluminum powder.

Another chronic issue that I found is the ignition switch. Most of the mid-2000s full-size GM vehicles have a faulty switch design and when it goes bad, your transmission defaults and gets "stuck" in 3rd gear. You have to pull the steering wheel to get the cowling on the steering column off. Happened to me and no problems since. $30 for the part and $30 for the tool.

The other chronic GM issue is bad stepper motors on the gauges and backlighting in the dash. Lights went out in my radio and part of the gauge cluster. The bulbs are soldered in so if you are good with electronics you can desolder and resolder in new ones. My CD player was having issues so I just replaced the stereo with a new aftermarket unit. The gauge cluster is being sent out today to have the stepper motors replaced and LED lighting installed.

 

[wookee]

That is the bearing that typically goes bad. I would check your diff. fluid and look closely for fine aluminum powder.

Turns out the previous owner ran the van a fair amount with little to no fluid left in the diff. I'm having to get a completely new one.

Once I get it back, I'll keep an eye out for the dash problems.