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Front Differential Bearings Bad

D

dunhavn

GUEST
Hello,

Just got my Avalanche Z71 back from the dealer today for service on the front differential bearings. I have 11,000 miles on my vehicle and this is the first major repair to have happened.

At around 9,000 miles I began to hear popping coming from the front end at low speeds (5 to 15 mph). This was there intermittently, but after 2,000 more miles it became an every day occurence that was becoming very loud.

The repair sheet states:
Front Diff--Case and Pinion bearings scored and pitted--replaced bearings--cleaned carrier housing--reassembled--road tested ok.

The time for this repair work was one day.

I have read several other posts concerning something similar. I am new to 4x4 and have ordered a service manual to understand them better. That is back ordered right now.

Is the transfer case and front differential the same or are they different?

I wanted to post this to share my experiences with the Avalanche.

Thanks

 
Thanks for sharing you experience with front diff problems. You're not the only one - so far mine's OK, but I'm surely going to watch it.

The front diff and transfer case are two different items. The transfer case hooks up behind the transmission. Out if it come two drive shafts - one to the front diff, one to the rear diff. The transfer case does the shifting between 2Hi, 4Hi, and 4lo. Crawl under your Av and take a look - there's plenty of room!
 
Just curious, if the transfer case is in 2WD, how did the bearings go bad or maybe you drove it in 4WD Auto? I don't think the front differential turns in 2WD so I'd probably never know I had a problem until too late...ie big mud hole :rolleyes:
 
I think . . .

That even in 2wd the half-shafts and the outboard bearings in the front axle / differential assembly turn all the time. When in 4wd auto, the half shafts are locked into the internal differential gears and now the front drive shaft is turning as well. Then when slip is sensed, the transfer case can shift into 4wd and complete the connection. Of course, shifting into 4hi or 4lo does both - locks the halfshafts and shifts the transfer case.

This setup is not as fuel efficient as the old manual locking hubs - where the connection was broken at the front wheels when in 2wd (half-shafts not turning), but it sure is more convenient than getting out in the muck to lock hubs!
 
It actually made the sound worse in two wheel drive mode.

I first noticed it in two-wheel drive. I had only used four wheel (auto 4 wheel) drive in heavy snow a couple of days and no other time.

The noise was almost non existent in 4 wheel drive.

That is what had me confused also.

Can anyone shed any light on this?

Thanks for the description between transfer case and front differential. I crawled underneath to take a quick look and all I see is plates protecting those areas. I will take time to take a better look and unbolt those protection plates.
 
wrchism, I'll bet you are correct on the front axels turning...I just got this AV and in the past I've always had manual hubs on my trucks and my brain wasn't into a "new" gear so to speak..! Thanks.
 
member named Butch (a fellow CT guy!) also had a front diff failure, at 1800 miles no less - he said the front diff always turns, in 2 or 4 wd

so now I check the rearview mirrow for blue smoke at startup, listen closely as I drive away in the morning for "front diff failure", check the rear seat area after rain for leaks - you guys are makin me paranoid!
 
Yep.., Half Shafts.., Drive Shaft., and Ring, and Pinion turn all the time., in Two Wheel Drive.., or 4 Wheel Drive.., on mine I began to get a Rumping noise in 2 Wheel drive.., and a Rumbling noise at low speed (5mph) in 4 Wheel Drive.., I saw that the Drivers side Half Shaft Stub axle was wobbling when I had the truck up on jack stands.., when the Dealer took it apart.., they found.., Bearing Shot on Drivers side Stub axle.., Ring, and Pinion Worn., and a Crack in the Case., they put in a New Front Differential.., ill drop the Gear Lube at 500 miles to see how it looks.., and be listening carefully to it..., they did have it done in One Day though.., I was Surprised.., Im going to talk to a place that does a lot of Racing, and Hi-Po Rear End work here.., to see what they know about this Unit.., Hope its not a weak link.., but anything can be made Better, if need be..... ;)
 
I hear Ya jack Buddy.., listening for Front Diff. noises., Listening for Engine Knocks.., checking Oil Consumption.., Draining, and checking Rear End (which is ok) thankfully.., Feeling for Wet carpet..., My Buddy who just bought an Avalanche owns one of the Best Transmission shops in the area here thankfully..., and Im going to put a Whipple Charger on this.., think it will stay on the work shop floor awhile longer...., LOL
 
:cautious:I have seen alot of posts about bad differentials.
I suspect I have the same problem (8/01 Production date).
How many complaints does it take for chevy to put out a TSB on this problem. The front drivers side has a harmonic sound that you can hear at 30-45mph in 2WD. And it's louder in auto 4WD.
I suspect it's the ring & pinion gears.
My dealership service dept doesn't hear it at all
:mad:. or hears it but pretends not to. Can I bring it to a GM tech?
I live in northeast PA. Any ideas?
 
Wow, this paranoia is contageous ;D I know that I'm on the trouble section of the site, but does anyone know of an AV that has something like 30K miles on it and no trouble? I only have 1300 miles on my Z71, it has TX in the VIN and is an 07/01 build. Sounds like I'm doomed from the start..!

I had a '91 Toyota 4 cyl 4WD that had 228K totally abusive miles on it when I sold it this morning, approximately $1700 spent on it in that period and not a single trip to a dealer while in warrenty. I wanted something bigger and more comfy so thought the AV was my best choice, but now I'm having second thoughts. I had dependable and expected it again. Guess only time will tell but reading this stuff is damaging my confidence.. :cry:
 
True venado.., but Manufacturers are Technicqally changing these New Vehicles alot now., I know a Friend of mine who bought a New Toyota truck., and has been to the Dealer 5 Times already with Engine, and 4 Wheel Drive problems., but its best to get these problems sorted out now.., while the vehicle is still under Warranty.., and enjoy it for the long haul. I bought My 89 Blazer with 10k miles on it.., the previous owner had it back to the Dealer twice for warranty work.., I lifted it, and did alot of other Mods to it.., and other than normal maintenance items.., Brakes, Shocks, One set of Ball Joints (Because of the Lift, and Tires) it doesn't owe Me a Dime, over 100K miles on it., did fix a couple of small rust spots, and Paint it two years ago, looks like the day it was New Still, and Runs like it two.....
 
My Avalanche is currently in the shop for a second attempt to fix this problem. So far, the story goes like this:

1. I noticed a metal-to-metal rubbing sound coming from the front end.

2. I took the truck to the dealership.

3. The truck was returned to me "no problem found."

4. I took the truck back the next day and road tested it with the tech. I pointed out the noise. A few miles later, he admitted he could hear it too.

5. Several bearings and seals in the front differential were replaced.

6. Got truck back and took a trip to Wyoming. On the way there, I noticed gear oil was being sprayed all over the driver's side of the vehicle.

7. Had truck checked in Wyoming before returning home. Dealer there found gear oil leaking from the differential's vent tube that extends into the engine compartment. The gear oil was dripping onto the driver's-side front axel where it then drained into the wheel. The wheel subsequently sprayed the oil all over as it spun.

8. Dealer in Wyoming suggested that the differential was over-filled when it was repaired. They checked the fluid level and sent me on my way.

9. More oil spray on the way home.

10. Took truck back to original dealer to have the mess cleaned up. They told me it was nearly impossible to overfill the differential to the point that it would vent the oil.

11. Dealer called and said bearings are shot again and they have no idea why. I'm now driving a loaner car while they figure it out.
 
Hey snowman,
The noise from up front, did it sound like a chirping sound intermittently? I have a similar noise, but only if the temperature is above 50 degrees and the truck warms up. On bumpy roads I dont hear it, but on a smooth road with slight deviations, it chirps like a bird, metal against metal sound.
 
More bad luck with the front differential. Yesterday I noticed a puddle of differential fluid near the driver side front tire. Took it to the dealer this morning and they had to replace the front left axle seal again and refill with fluid.

Also, while they were working on it they noticed that the remote key fob would not work anymore and had to order a replacement for that. A battery change and reprogramming would not fix the problem.

Hopefully this is fixed now.
 
If it matters my build date is March 2001 as stated in the upper right hand corner of the sticker on the driver side door.

I wonder if this is the first month they started building them?
 
Ahhnuld: The noise was not a chirp. More like a scrape. And it was continuous once it started.

Anyway, I've got the truck back. Front differential has more or less been completely rebuilt with new parts. No noise. No leaks. Let's hope it stays that way.
 
Aegis said:
I see a "born date" of 3/01...Is this true?? I had no idea that the Av's were out that early...
Click to expand...

Can anyone else verify this?

Could this be a misprint on my sticker?

Is there any other way to verify my build date?

Thanks for any help. :)
 
Please Help!!  My Av is at the dealer for what I  think is the bearings in the front differential going bad and they said they can't find anything wrong!! :E:  My dads AV already had them replaced and mine is now making the same noise.  If it is possible does anyone have a TSB number I can give them to lool up? 

Thanks

Pogo
 
How many miles do you have on your AV right now?

-James. :cool:
 
I only have 13,500 on it. My dads went at about 12,000.  I know of another one that had the bearings replaced at about 20,000 and just had the wheel bearings on the drivers side replaced at 50,000!!
 
Anyone with the TSB?  I just got off the phone with the dealer and they can't hear the noise :E:  I'm sure if I go over there and take the tech out for a test drive I will hear it...

Sorry, just frustrated and ranting a bit

Pogo
 
Differential bearings, front and back, are a major problem with Avalanche and similar GM products.  There should be a recall started sometime soon.  Numerous complaints from everywhere.  Class action suit under serious consideration right now
 
There is a major design defect that existed when these trucks left the assembly line.  A recall or class action suit are the only answers I am afraid. 
 
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