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

[machadosl]

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.[/QUOTE]
Hi Viking, well after adjusting and of course replacing the lockers, for safety precautions I used a screwdriver to make a very small puncture in three points of the the screw lane where the regulator nut slide. You do not need to damage the lane, it is only a small puncture that do not allow the castle nut to slide out of its position. I have learned this with an engineer of aeronautical machines. Well until there the differential is fine.
For the second question, yes, you can just replace the bearings, if you have everything in hand this service can be done in a day if it is your first time, on the second time it will take not more than 4-5 hours. Yes, I have been repairing the front differential of my friend's cars.
Well, if you have more questions, just ask. And sorry for my writing, sometimes I just do not know the correct word.
Cheers

 

[Nutter]

Related: Front Axle Disconnect on a 9.25"

Like so many others here, I am enormously grateful to bigredmariner for the time and detail in the original post. Awesome!!

Situation: 2008 Silverado 2500HD with the 6.0, lost 4WD trying to drag a camper trailer out of a Wadi (Creek) in Oman. Trying to skull drag it at the time with a chain and thought the sound was the links in chain finding their happy place when the tension came on. Unfortunately - not!

Thanks to the original thread and details included, I managed to extract and strip down the front right axle tube. The disconnect sleeve had detonated and the yoke had also broken.

There are some small gouges in the clam shell inner housing (Pumpkin), perhaps 1mm deep at most. There are some raised edges to those gouges that I plan to sand down before installing the replacement parts.

I purchased a disconnect replacement kit, and a new axle output shaft. The splines on the end of the output shaft took a hammering and I needed a good gear puller to get the broken sleeve off the shaft! I understand that this is quite a common failure, so I hope that the pics may help someone trying to sort this out themselves.

I suspect the cause's were;
Abuse from the previous owner (this was my first trip in my new/used truck), and
I suspect, no oil changes EVER in the front Diff [approx 60,000Mi (101,000km)] - stuff that came out - thick and pitch black!!

There are pics below. How the part should look (replacements) and how it all came out :-((

Question: Should I change the axle seal as a natural course of action whenever the shaft is removed from the axle tube, or can I just place the axle back in? I am a little concerned that some metal particles may have made their way down to the output shaft bearing, which I can't replace without replacing the seal. I have a new bearing in the disconnect kit - but keen to get an answer from those more in the know. Also, I am assuming that endplay for the shaft is not an issue during a direct replacement? Just pop it in, lock tab washer, washer, split ring, done? Correct?

Cheers
(New Zealander living in UAE)

 

[Bigredmariner]

Like so many others here, I am enormously grateful to bigredmariner for the time and detail in the original post. Awesome!!

Situation: 2008 Silverado 2500HD with the 6.0, lost 4WD trying to drag a camper trailer out of a Wadi (Creek) in Oman. Trying to skull drag it at the time with a chain and thought the sound was the links in chain finding their happy place when the tension came on. Unfortunately - not!

Thanks to the original thread and details included, I managed to extract and strip down the front right axle tube. The disconnect sleeve had detonated and the yoke had also broken.

There are some small gouges in the clam shell inner housing (Pumpkin), perhaps 1mm deep at most. There are some raised edges to those gouges that I plan to sand down before installing the replacement parts.

I purchased a disconnect replacement kit, and a new axle output shaft. The splines on the end of the output shaft took a hammering and I needed a good gear puller to get the broken sleeve off the shaft! I understand that this is quite a common failure, so I hope that the pics may help someone trying to sort this out themselves.

I suspect the cause's were;
Abuse from the previous owner (this was my first trip in my new/used truck), and
I suspect, no oil changes EVER in the front Diff [approx 60,000Mi (101,000km)] - stuff that came out - thick and pitch black!!

There are pics below. How the part should look (replacements) and how it all came out :-((

Question: Should I change the axle seal as a natural course of action whenever the shaft is removed from the axle tube, or can I just place the axle back in? I am a little concerned that some metal particles may have made their way down to the output shaft bearing, which I can't replace without replacing the seal. I have a new bearing in the disconnect kit - but keen to get an answer from those more in the know. Also, I am assuming that endplay for the shaft is not an issue during a direct replacement? Just pop it in, lock tab washer, washer, split ring, done? Correct?

Cheers
(New Zealander living in UAE)

Thanks for the kind words Nutter.
If you can get the seal relatively easy where you are then I would go ahead and replace it and do the bearing. If you're looking at a long wait and a bunch of money you could try to wash out the bearing and housing to remove any metal particles.

Yes, you're correct on assembly too.


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[Nutter]

Done!

Cheers Bigredmariner!!!

"Got 'er dun!!"

Secured a new seal - they had one in stock!! Awesome! AND they chucked it in with the Axle Output Shaft (because I helped the guy with an idle vacuum issue on his Charger, parked in front of the shop - win!! Sometimes you just have good days.)

Anyway, she's all back together and torqued to the specs in your .pdf. The bearing in the disconnect kit from AAM is for the inner stub axle - under the adjuster. I popped the outer bearing out of the tube and cleaned it out. Some little bits, but pretty good really. No pitting. No strange noises compared to the other, similar bearing in the kit. No choice but to pack it back in and follow up with the new seal. Had to tweak the adjuster down a tad too, in the disconnect housing on the 'pumpkin' side - seems the shrapnel churning around in there may have knocked/lifted it a bit, and I did not want to take the chance. Good heads up if someone else has the axle disconnect shatter on them too?!!

Anaerobic Sealant is impossible to find here. I did get some High Temp RTF and used that on the mating surface. Hopefully it will work. I was that keen to get it together before the stuff went 'off' that I forgot the washer between the engaging gears for the disconnect. Had to pull it back off and try again. Fortunately I hadn't put any bolts in it yet.

If anyone faces the same, "seemingly common", problem with the disconnect damage, I found the Disconnect Replacement kit on eBay for US$150 (Drivetrain America). It is made by AAM - the OEM manufacturer. The output shaft? The cheapest I could find on eBay was US$225, but it can be found for as low as US$176 on some GM parts sites in the US. Would have cost me US$300 total to have it shipped here within three days. Managed to get a new one locally for US$231, with the axle seal thrown in. Happy days...

Anyway, the job would not have been possible without your thread and the time that you put into producing this. I am incredibly grateful to both you and the site. Now the 'daily' is sorted, I can ease springs and get back to working on the '73 K10 ). Expect more questions in the future ;-)

Thanks

 

[black79ta]

Hi guys, just an update on my AWD 2004 front diff rebuild (did mine in June 2014), I posted on page 8 #79,#80 with my specs. To wrap up my rebuild, when I test drove it the grinding was gone, but there was a howl. my tires were cupped etc. I finally got new tires and the front diff is quiet as a mouse. SUCCESS!! I was going to swap out the tires from my new Silverado just to see if that made a difference but never got around to it. I have about 15k on the rebuild. no drips. Great thread. Someone else commented that they could not really determine the backlash until the case was torqued together. That is what I experienced. Once the case was torqued together the backlash was very evident and measurable.

 

[Wolfman86]

pdf location

Bigredmariner could you share the line to the pdf you were talking about. I cant seem to find it. Thanks

 

[afterburner]

Many thanks to bigredmariner. I just finished re-assembling my son's 2002 Z71 front Diff. We had to replace the carrier, as one of the carrier bearings was destroyed. It spun on the carrier and took out the lock ring too. We noticed a lot of play in the driver side shaft, the wasted bearing was on the pass side of the carrier. Oil was changed 3000 miles ago with Castrol Synthetic, and the old oil wasn't alarming at that time.

Here are a couple of tidbits that others may find helpful, and if I did anything wrong, I hope someone will let me know!

1. Definitely get new locktabs. The used ones were too sloppy to knock down and stay. They are about $1.50 each full retail. And they knock in really nicely.
2. If your tabs don't line up with the notches, the entire adjuster ring can pop out and be re-set a few degrees one way or the other. You will have to set your preload on the carrier again, but at that point, it's really easy to do. Check your backlash again, as it may change a little bit. Mine did.
3. I had to torque the carrier preset to just over 55 lbs to get enough increase to the rotating torque.
4. I was surprised how much torque you actually have to put on the bearings to get the preload. The pinion was actually quite stiff, and would not rotate freely at all if spun. And that was at 19 in lbs, measured with a 1/4 drive torque wrench. Total rotating torque, without seal was 32 in lb.
5. The pinion depth was fine and the pattern was remarkably good.
6. The seal added about 1 in lb to the rotating torque.
7. I made a tool to adjust the lock rings. I welded a bolt to a piece of plate and used a welding glove to hold it firmly down while I torqued it.

It is now a tight diff with no play, and very little gear slop (backlash). Having never rebuilt a diff before, my main worry is that it is too tight. I don't have a feel for them yet! We're just going out to put it back in the truck, so we'll see how it performs.

 

[Namecips]

This is a great thread. Had to join the site just to say that.


I've had an issue with my front differential for about 6 months now.


First mechanic said it was a bad transfer case and chain had stretched out and was knocking on the wall of the case.


Second mechanic threw his hands in the air and said "you got me".


Third at least found the problem. He took the unit apart and stated the locking tab was to loose and was not doing it's job. He put a new bearing in and "fixed" the locking tab. Well, I got on to the highway and didn't get a mile down the road before the clunking/chattering started again.


Is this a common problem with these units? Would tack welding the locking tab in place fix the issue?


Any other suggestions? I'm no mechanic, but I'm an above average DIY'er and would love to be able to fix this myself.


Any help, suggestions or thoughts would be greatly appreciated.

I have a picture, but for some reason can't upload it. It's on my desktop, but when I click insert image, it asks for a URL.

 

[Namecips]

double post - please delete

 

[Bigredmariner]

This is a great thread. Had to join the site just to say that.


I've had an issue with my front differential for about 6 months now.


First mechanic said it was a bad transfer case and chain had stretched out and was knocking on the wall of the case.


Second mechanic threw his hands in the air and said "you got me".


Third at least found the problem. He took the unit apart and stated the locking tab was to loose and was not doing it's job. He put a new bearing in and "fixed" the locking tab. Well, I got on to the highway and didn't get a mile down the road before the clunking/chattering started again.


Is this a common problem with these units? Would tack welding the locking tab in place fix the issue?


Any other suggestions? I'm no mechanic, but I'm an above average DIY'er and would love to be able to fix this myself.


Any help, suggestions or thoughts would be greatly appreciated.

I have a picture, but for some reason can't upload it. It's on my desktop, but when I click insert image, it asks for a URL.

You can get new lock tabs from the dealership. Read this copied post from another user in this thread, he lists the GM part number and all. Also you can use locktite on the adjusters.
"I just wanted to say thanks for this thread. I attempted this this past weekend, front and rear 4.88s. I had never installed any gear sets before, the idea wasnt too complicated but i ran into quite a few issues that held up progress.<br />
<br />
One thing i did is drianed both axles then filled them with diesel fuel. Then i drove it around the parking lot for 5 minutes to help clean the Red Line Heavy Shockproof oil i had it in. I wasnt worried about bearings since i was replacing them all.<br />
<br />
When i opened the rear up i could move the carrier left to right 1/4" with it bolted in. I could rotate the pinion about 1/8 of a turn before engaing the ring gear. All of the bearing rollers and races were the texture of asphalt.<br />
<br />
I couldnt get a good wear pattern at all on the rear axle, pinion was too deep but after some searching by myabe .006" on a similar gear/setup pattern i saw online. I tried every shim combination i had and even measured the pinion bearing height vs the new one (i machined the center from one) and found the checking bearing .008" taller and shimmed accordingly when i installed the final bearing. i ended up with .009" backlash which gave me a better pattern. I am using USA Standard gears which i understand are yukons that didnt make QC anyway so i figured it was the best i could do.<br />
<br />
The front axle i tried for 2 hours to get the short stub axle out. I tried every combination of assembly, penetration oil, 10lb slide hammer, rubber mallet, 4lb hammer etc to get it removed. I even took it to a shop to get the axle out. They tried for an hour, then finally got it out with a slide hammer by wrapping a strap around the hammer slide and pulling as fast as they could.<br />
<br />
After all that the front was easier than the rear. I got new locking tabs form GM PN 15588312 about $1.40 from the dealer, after reading the horror stories about them breaking, i put blue thread locked the threads of the adjusters, not sure if it will hold or make a difference but i dont think it could hurt it. I did have trouble crushing the crush sleeve on the front, the rear went fine, i used an impact, the front, i could not get it to crush. I had to crank my compressor up to 135psi and i have an air cat 1150 (supposedly 975ft lbs tightening at 120psi) to finally get it to crush. I removed the pinion to install the seal (i saw it suggested to get roating torque without seal first), and when i removed the pinion all of the rollers and cage fell out of it. It was a Koyo bearing, none of the race was dented or anything. I ordered a timken, and installed in place. I had a great wear pattern on the front, then i installed the new bearing and it went a few thousands deeper. I didnt worry about it too much, i was already 30+ hours into this job.<br />
<br />
For the rear 4.88 gears i had to grind one tooth of the ring gear to get the cross pin back in.<br />
<br />
I cleaned everything with brake clean, all new bearings housing etc. I replaced the axle tube bearings and seals. I filled the rear with oil, rotated it around 20 times then drained it since i had it apart 12+ times and im sure it got some dust and dirty in areas i couldnt clean out. I also rotated the front and rear pinion, and eaxl axle 50+ times in each direction once filled to ensure all bearings were oil before anything was put under load.<br />
<br />
the front stayed clean and i had it apart maybe 5 times.<br />
<br />
I bought the yukon tool though i dont think that you need it. I just kep loosening the case and making adjustments with my fingers until i had the correct backlash and preload. I sealed the case with the suggest 1184 (1194 has been replacedby 1184) and thats come good stuff. Says it's ready for gear oil in 20 minutes.<br />
<br />
I filled both front and rear with just dino 80w90 oil for now. I will drain in 500 miles and put in some red line, a mixture of 75w90 and heavy shockproof i think.<br />
<br />
There is a faint whine at cruise around 55mph when the gears warm up, Wehn cold i cant hear anything at all when it warms up its a faint whine but nothing bad at all, nothing like it was or anything that bothers me too much. I figured with a less than ideal gear pattern it would be a littel noisy, its actually pretty quiet, 4,88s are low gear anyway so i think they'd make a little more noise. I think with some run time and heavy shockproof the noise will go away. i only put maybe 1,000 miles a year on this (2001 suburban) and i tow my bobcat maybe 100 miles locally throughout the year. I think it will be ok.<br />
<br />
With the rear gear i ended up leaving the pinion deep, any of the other adjustments put the pinion high on the tooth top land, right now its about 2/3 down towards the crown, and centered for the most part heel to toe, maybe a little towards the toe on both axles. There is a definitely line in the root on the rear but its not far down in it, i couldnt get it to go away without the pattern being on the top land of the gear so i just let it be.<br />
<br />
I'll let you guys know if it blows up haha. I think it'll be ok, i'd rather the pinion be deep than shallow anyway.<br />
<br />
thanks again for this awesome write up!


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