Rear Differential Rebuild

[jpetree85]

Hi All,

I've done some searching and I have not found a topic like this, if it already exists, please point me in the right direction.

I was trailing, trying to climb a hill in 4Lo when my rear diff literally exploded. This topic is two questions:

1. Is this common on a stock 8" rear with 3.42 gears?
2. What all would I need to completely rebuild the rear diff from the ground up?
2a. Are there better gears/tips or tricks to prevent this from happening again?

Thanks to all in advance.

[TBYODA]

Pettree do you have a G80? It has been noted on the site that the 8" G80 is pretty weak. Personal I'd skip the rebuild and get a new stronger 8.6" rear axle out of 06+ ext or 5.3l. R ever better yet 9.5 out of a SS stock gears are 4.10. Check out www.car-part.com, as far new gears you will need to do your research here cause the front diff replacement is a PITA. What tires are you running?

[jpetree85]

No, I do not have a G80. A rod literally blew out the cover. I want to do a 8.6 swap but don't know what all I need. Obviously I need the axle housing, axles and gears. I am also looking at a locker. What else do I need? I don't want to go 9.5 due to drive shaft mods needed.

[TBYODA]

The 8.6" is bolt in, you just need a 06+ ext or 5.3l 8.6" with 3.42 gears axle. Assuming you stay with the same gears if you get a open diff you could install lunch box locker. Like a lockright, many members have used them. Research man.

[Trail X]

Would be a good time to regear. If you don't, you'll be kicking yourself later.

[Shdwdrgn]

I'd have to agree, you need to buy a new one anyway, might as well bite the bullet and re-gear. If you can find a complete 8.6" axle with 4.10's, you'll be really happy. Swapping the rear is pretty easy, I did it in an afternoon by myself with no previous experience on this platform. Just use a jack under the body to raise the vehicle up off the springs, and they'll fall right out.

Of course where you'll kill yourself is in swapping the front differential. For such a small unit, it will cause you no end of headaches. Took me 19 hours to disassemble and 3 hours to get it back on the road.

And FYI, you *can* swap out the rear and drive around for awhile before swapping the front if you change gears... just remember to never engage 4WD while your gears are mis-matched. I drove mine for about a month without any issues.

[jpetree85]

Thanks for the replies.

I am definitely going to swap the rear for an 8.6. Installing the lift, I became acquainted with installing the axle housing. However, the question still remains, what all do I need if I do a complete rebuild? Meaning, what parts? Axles, rebuild kit, new carrier, gears? Anything else? If I install a locker, do I need a carrier, or do they attach to a carrier?

Thanks for any input.

[Shdwdrgn]

Easiest for the rear is get a complete 8.6" axle (2006+). That way the gears are already set, and everything else is a direct swap. I used my original rotors and brakes because they were in better shape than what came with the axle. Find something with < 100k on it, and you'll be in good shape.

For the front, you can get a replacement from any year of TB/Envoy. Mine came from a 2007 SS (I think 4.10's were stock on them?) and it fit right in. The only thing you have to watch for is you can't use early 2002 (usually identified as 'single-hole'). Because of the scarcity, you could end up paying almost twice as much for the front diff as you pay for the rear axle.

Sorry, I guess this only covers what is needed for a direct swap, not a rebuild. I'm using the 8.6 G80, and I installed my parts directly as I received them, threw in some synthetic oil, and I was good to go. I didn't even crack open the front diff, I only took a peek at the gears through the oil fill hole.

[Trail X]

Of course where you'll kill yourself is in swapping the front differential. For such a small unit, it will cause you no end of headaches. Took me 19 hours to disassemble and 3 hours to get it back on the road

I actually found the front easier, but to each their own. I felt the rear basically needed two people due to the weight of the axle but it was quicker, the front I got done in like 4-5 hours but went pretty smoothly.

However, the question still remains, what all do I need if I do a complete rebuild? Meaning, what parts? Axles, rebuild kit, new carrier, gears? Anything else? If I install a locker, do I need a carrier, or do they attach to a carrier?

Are you saying that you want to take a junkyard axle and rebuild it? Why? Also, no offense, but if you're asking that question and not doing the research all on your own, then let's face it. You're probably not up for the rebuild job. It's one thing to bolt in a new axle. It's an entirely different endeavor to rebuild one, ground up.

If you do get a locker, the work required greatly depends on the type. Some pop into an open carier, some require setting up backlash and getting patterns.

The only thing you have to watch for is you can't use early 2002 (usually identified as 'single-hole')

Incorrect. They are all the same and all compatible as far as I've seen. We compared a few from 2002 and they were all the same.

[Shdwdrgn]

Incorrect. They are all the same and all compatible as far as I've seen. We compared a few from 2002 and they were all the same.

I know I've seen pictures of the single-hole style... but are you saying that the hole where the bolt actually goes through is the same in both versions?

When I did my rear axle, I put jack-stands under each rear door, then used a floor jack to hold the axle. Once I lowered it to where the springs fell out, I had enough room to just roll the floor jack right out the back. Then it's easy to pick up the axle by yourself (or just pick up one end and walk it around). Drop the new axle onto the floor jack and roll it back underneath.

I'm sure I could do the diff a lot faster the second time around, but I went into this with an incomplete set of tools and absolutely no previous experience with working on the front end of a 4x4 before. At least the rear axle was similar to when I swapped axles on my '74 Pontiac. Oh yeah, I also rebuilt my disconnect while the front end was apart.

[Cable810]

I've got a 2 hole front diff in mine.

[Moots1288]

Of course where you'll kill yourself is in swapping the front differential. For such a small unit, it will cause you no end of headaches. Took me 19 hours to disassemble and 3 hours to get it back on the road

I actually found the front easier, but to each their own. I felt the rear basically needed two people due to the weight of the axle but it was quicker, the front I got done in like 4-5 hours but went pretty smoothly.

However, the question still remains, what all do I need if I do a complete rebuild? Meaning, what parts? Axles, rebuild kit, new carrier, gears? Anything else? If I install a locker, do I need a carrier, or do they attach to a carrier?

Are you saying that you want to take a junkyard axle and rebuild it? Why? Also, no offense, but if you're asking that question and not doing the research all on your own, then let's face it. You're probably not up for the rebuild job. It's one thing to bolt in a new axle. It's an entirely different endeavor to rebuild one, ground up.

If you do get a locker, the work required greatly depends on the type. Some pop into an open carier, some require setting up backlash and getting patterns.

The only thing you have to watch for is you can't use early 2002 (usually identified as 'single-hole')

Incorrect. They are all the same and all compatible as far as I've seen. We compared a few from 2002 and they were all the same.

You're welcome hahaha

[Trail X]

Incorrect. They are all the same and all compatible as far as I've seen. We compared a few from 2002 and they were all the same.

I know I've seen pictures of the single-hole style... but are you saying that the hole where the bolt actually goes through is the same in both versions?

Maybe that's what I was thinking. I just remember the outcome of that discussion was that it was a moot point.

You're welcome hahaha

Yeah, I have both you and Regulator to thank on that one.

[navigator]

I think the confusion is in that in 2002 there was a trailblazer badged s10 blazer that has a different front diff.

[Shdwdrgn]

I think the confusion is in that in 2002 there was a trailblazer badged s10 blazer that has a different front diff.

I just hit google images, the diff from the blazer has a completely different housing.

[Moots1288]

I think the confusion is in that in 2002 there was a trailblazer badged s10 blazer that has a different front diff.

I just hit google images, the diff from the blazer has a completely different housing.

Our housing is aluminum and there's is steel.

[jpetree85]

The reason why I am asking is because I am finding a complete replacement. However it's used. When I get it I want to look at it and see if it's damaged. I am preparing for the worse case scenario. From the research I have done, I would need a rebuild kit and gears. I plan on putting a full detroit locker in the rear, so it is the carrier. If the axles are damaged, the obviously those too. This is what I found during my research, but I want to verify as I have never had to rebuild a differential. Engine and tranny, yes. Other drivetrain, no. Thanks for the replies.

[Trail X]

Where are you getting this axle from? If a junkyard, it should be good to slap in and run. The bearings are norally good for a long time, and the only ones potentially at risk are the wheel bearings. Now if you want to put in the detroit, you will potentially need shim packs for your new carrier. If you are also regearing, you need gears (obviously) and there's a potential to need need pinion shims. You don't really have to replace any bearings unless they are pitted or oddly worn. Anytime you are messing with the gears though, you will need a few non standard tools mag base dial indicator, in-lb torque wrench, bearing splitter, and gear marking compound. I probably missed something.

[Shdwdrgn]

If you are buying from any place that ships, I wouldn't buy from anywhere that doesn't state they inspect the unit before shipping. You're going to pay a LOT for the shipping costs, you do not want to have to return them! My rear axle came from an internet junkyard site, and the front diff came from ebay. In both cases, I was able to ask questions before buying.

Also, this hasn't come up yet, but if you do plan on changing your gears, locate someone with programming software (HPTuners, EFI-live, etc) that can change your speedometer settings. Most people are finding that GM will not help, even if your dealership makes the call. If you can't find anyone closer, let me know... I have HPTuners, but there's a one-time $100 license cost for each vehicle.