Rebuilding A GM 8.25 IFS Differential **56K Beware! Pic Heavy**

flyerfly

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Thanks for the wonderful write up. One question though... is it possible to remove the driver side stub shaft without splitting the case? I have tried slide hammer, large pickle fork supposedly meant for this to no avail. I removed the diff from the truck and tried to split the case but it will not split... Someone suggested cutting off the flange from the stub shaft so that the case would split and then replacing it...is this the only way?! :facepalm::( It does not look like I can get to the cir clip from the vent hole either... Any info would be really great.
 

machadosl

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Hi flyerfly, it is possible to remove the side stub without splitting the case, you will only need a polyurethane hammer to hit on it. When I disassembled the diff of my car first I take it out, drained the oil and then I used the hummer to hit the side stubs, after that I started opening it.
 

flyerfly

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Well it finally came out when taken to a professional shop...they broke it taking it off. The flange broke/bent basically. Once it was fixed and a new cir clip was put in it comes out with a gentle tug....That little design flaw cost me $360 ($110 for the shaft and $250 labor) :fume:
 

Pdl07z71

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Well, i took out the Differential and attached the axle tube and installed this weekend, sounded good saturday night and sunday morning. My wife took it out of town, and says its making a noise. I took a test drive this morning and there is a sound i'm not sure what yet. When i come to a stop its more of a winding down sound, almost like tires (could be, but i didnt' here this the day before) , maybe more mechanical. I plan to test drive again tonight. It's probably nothing, but i wonder is putting the new diff in might of awaken another problem, like CV joints? I did not replace the needle, i know..I Know.....there was only one i could see, and it looked and felt fine. Also when i poped the tube/axle out with a rubber mallet i assumed the snap ring stayed in the groove, because it was not on the shaft. When I put the shaft in, it did stop, and i had to smack it back in. Any thought????


You raise an interesting point that I think I can shed at least a little light on. I am in the process of replacing the right front axle seal on my 2004 Tahoe Z71. In doing so, I relied on different sources that said I could simply drive the axle out of the extension housing, replace the seal and reinstall. Great. Well, that's not what I experienced. Why? Because my right axle is held in by a ring clip that MUST BE RELEASED FROM THE AXLE BEFORE THE AXLE WILL SLIDE OUT OF THE TUBE. I drove my axle out with brute force and the ring clip damaged the thrust washer and tabbed washer that prevented the axle from sliding out. See below. This is what I found inside the extension housing (the damaged washers are in upside down in the pic. the tabbed washer seats into the grooves and the flat washer goes on top of it) after I beat the hell out of the axle to get it to release:



DSCF7076 by rzgkane, on Flickr


There seems to be two types of right axle setups in these vehicles. Making matters more complicated is the fact that the GM parts system, using my VIN, thinks my truck has a different setup than it does. To illustrate, look at the images below. The top image (which I believe is of a 9.25 axle) is exactly what my setup looks like. The bottom image is what GM says is in my Z71 and what most other owners have found inside their 8.25 front diffs.


Notice that there are two washers (#5 and #6) behind the axle's retaining ring clip (#7)? Well, if you drive the axle out using force, those two washers will become damaged and will fall out of place. If you simply slide the axle back in after replacing the seal and you think you are done, wrong, those washers (and maybe even the ring clip) will be bouncing around inside the extension tube. Luckily, the ring clip stayed on the axle and prevented me from being able to slide the axle out past the outer bearing. That forced me to remove the extension housing and discover the damage inside. You probably were not so lucky.



2004 Tahoe Z71 Front Axle Housing by rzgkane, on Flickr

The image below is what GM thinks is in my truck. Notice the gear #6? That does not exist in my vehicle. Numbers 6 and 8 are a one piece unit in my truck and are depicted as # 8 in the top image. That gear (#6) is what the axle's locking ring sits in and can be released by simply prying the axle out. The locking ring usually stays inside the gear and re-engages the axle when the axle is tapped back in. Nice for folks with that setup.






Why is the GM parts system confused? I don't know. But the parts guy at my local dealer looked at the extension housing that came off my truck (I am the original owner and no work has ever been done to the front diff) and noted that it had "K3" cast into it. He says that K3 is consistent with a 1 ton truck, not the 1/2 ton that a Tahoe is. Hmm. Crazy. But facts are facts. My 2004 Z71 has different insides than what most other 8.25 diffs have and I suspect others out there have the same issue.


Moral to the story? If you have a 2004 Tahoe Z71, I suggest you remove the extension housing before trying to drive the axle out of the tube. You don't know what's inside until you get in there.


Hope this helps someone.

Sorry to dig up an old thread, but I have the same situation. I have an 07 NNBS Silverado and I also have the thrust washer and locating ring, not just the one washer listed in the part diagram. (I have #5 & #6 in the image above) I need to replace them because I also bent the crap out of them. Does anyone happen to have the part numbers for these? I can only find diagrams and part numbers showing the one single #5 washer that is incorrect for my application.

Thanks
 

machadosl

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Hi, well, when I disassembled the front differential of my 2003/04 Z71Suburban I followed the steps described here, driving out the axle using a rubber hammer. As you can see in the picture below the axle of my car looks the same of your car. You can notice that the washer is a little bit outworn, but it is fine. I suppose GM has put a clip that is thicker or you had tried to remove the axle hitting it only on one side. Well, as I always say: "There are thing that only GM makes specially for us!". Hahahahaahahahahahaha Sorry for this joke.
Here is the photo:
2ufaro7.jpg

And here are the photos I took when I was adjusting the differential:
2hgqluh.jpg

213j71l.jpg

35jez5g.jpg

And after having it adjusted I have made a puncture on the screw to fix the adjustment, as i do not trust on the system that GM has used to maintain the adjustment.
289frbk.jpg
 

Bigredmariner

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Guys thanks for adding your findings to this thread. It may be an older thread but there is a ton of info that's been shared here.


Posted from my iPad via Tapatalk HD.
 

kmk7199

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Great post bigredmariner. Was gonna take my 99 gmc z71 (newer bodystyle) to shop to have bearings replaced , but after Goin through your instructions several times I built up the courage to tackle it own my own . I am a machinist , NOT a mechanic by any means , but this seems right up my alley . A couple things have me scratching my head a little , but I feel like once I actually have differential apart it will all make sense . I have access to the machine shop I work at 24/7 where I will have everything I need for this job in arms reach . Received Timken bearing rebuild kit yesterday and am starting work in the morning . If any questions arise , hope you are available to spread your wisdom to a rookie . Once again , great post .
 

VikingTrad3r

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Question regarding newer lock tabs to hold carrier bearings in place

Hi All,

Bigred, thank you so so so so much for the time you took orginally to publish this thread. And, in following up with people afterwards as they carried out the repair themselves. I am in that camp and about to start myself. I have an 06 awd denali xl, fulltime awd.

My question is weather or not there is an updated lock tab setup. My understanding from reading in multiple forums is that the reason these diffs eat themselves is because the locktabs fail, which allow the carrier bearings to "unseat" or "walk" out a bit which causes excess play and then the bearings fail. If caught early enough, my understanding is that the carriers and lock tabs may be the only required parts to be replaced....IF...its caught early enough.

Anyway, to my question, is if you or anybody else here has found a location or a part number from gm where we can buy the updated lock tabs for the 06-prior carrier bearings?

Do these exist?

Thanks All,

I spend most of my time over at corvetteforum.com but it appears that my wifes denali xl requires this repair. Cheers,

VikingTrad3r.
 

Bigredmariner

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Hi All,

Bigred, thank you so so so so much for the time you took orginally to publish this thread. And, in following up with people afterwards as they carried out the repair themselves. I am in that camp and about to start myself. I have an 06 awd denali xl, fulltime awd.

My question is weather or not there is an updated lock tab setup. My understanding from reading in multiple forums is that the reason these diffs eat themselves is because the locktabs fail, which allow the carrier bearings to "unseat" or "walk" out a bit which causes excess play and then the bearings fail. If caught early enough, my understanding is that the carriers and lock tabs may be the only required parts to be replaced....IF...its caught early enough.

Anyway, to my question, is if you or anybody else here has found a location or a part number from gm where we can buy the updated lock tabs for the 06-prior carrier bearings?

Do these exist?

Thanks All,

I spend most of my time over at corvetteforum.com but it appears that my wifes denali xl requires this repair. Cheers,

VikingTrad3r.

Man that's a good question, unfortunately I have no idea if it even exists. If you do happen to run across an improved setup please post what you find in here. Thanks


Posted from my iPad via Tapatalk HD.
 

VikingTrad3r

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another question before i tear mine apart

Hi, well, when I disassembled the front differential of my 2003/04 Z71Suburban I followed the steps described here, driving out the axle using a rubber hammer. As you can see in the picture below the axle of my car looks the same of your car. You can notice that the washer is a little bit outworn, but it is fine. I suppose GM has put a clip that is thicker or you had tried to remove the axle hitting it only on one side. Well, as I always say: "There are thing that only GM makes specially for us!". Hahahahaahahahahahaha Sorry for this joke.
Here is the photo:
2ufaro7.jpg

And here are the photos I took when I was adjusting the differential:
2hgqluh.jpg

213j71l.jpg

35jez5g.jpg

And after having it adjusted I have made a puncture on the screw to fix the adjustment, as i do not trust on the system that GM has used to maintain the adjustment.
289frbk.jpg


you mention here that you do something with a scew because you do not trust the gmc lock tab system. i dont blame you as it appears that is the crux of the issue with these 8.25's.

Could you elaborate on what you are doing?

I have just picked up two new lock tabs from the dealer as i am assuming that one is broken. Do you have a better way of "locking" the carrier bearing so the preload stays put??

And second question,

If my ring/pinion are fine, which im am guessing they are, i have caught this early, could i just replace the carrier bearings and call it a day?

Thnx all.
 

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