H3 Front differential

[FloridaH3]

Does anyone know what other/if any other vehicles our front differentials came in? Or do I have to buy an 06 H3 specific front differential?


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[amrg]

The H3 diff is unique. Make sure you get one from an I5 as the Alpha has different gearing. Any 06-10 I5 diff will work, an adv model has the Cast Iron diffs which are a plus

 

[jphh20]

Our specific setup for the front diff assembly is unique to the Hummer H3. Are you looking to rebuild or source a replacement assembly? I am sure that many of the bearing and gear sets are common across GM.


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[FloridaH3]

Got some real bad grinding noises coming from inside it. Figured I would replace the whole diff.


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[jphh20]

Rock auto has rebuild and certified assemblies and you can find dozens on eBay or Car-Part.com. Trying to find a low mileage unit is always hard and tends to get a decent price. If you haven’t already, confirm it’s the diff by draining the fluid and pulling the cover to perform and inspection. Front end Grind noises tends to be difficulty to pin point.


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[FloridaH3]

Thank you! I’m replacing complete front suspension, and tack and pinion at the same time. She’s got 222k on her so she needs it anyway lol. I’ll pull the cover and check it over though before for sure.


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[FloridaH3]

Rock auto has rebuild and certified assemblies and you can find dozens on eBay or Car-Part.com. Trying to find a low mileage unit is always hard and tends to get a decent price. If you haven’t already, confirm it’s the diff by draining the fluid and pulling the cover to perform and inspection. Front end Grind noises tends to be difficulty to pin point.


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Do you know of any hummer specific differential rebuild pdf/video/guide? I see a bunch for for the fam 7.6 and 8.5 differentials but wasn’t sure if the internals would be the same since ours is unique.


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[JPaul]

Grab the pdf off of schwarttzy.com for the front differential, it has the procedure in there. The front diff uses the GM IFS 7.6 gears. (Edited because I remembered incorrectly)

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[FloridaH3]

Thanks so much man!


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[JPaul]

Btw, have you rebuilt differentials before? If not I would suggest taking it to a shop that specializes in it. It's not super difficult, but it's still something even I shy away from since if you do it wrong it will fail quickly. Only two things I won't mess around with. Automatic transmissions and differentials. Someday I'll probably take a crack at it, but I like having reliability on a vehicle I plan driving long distances.

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[4speedfunk]

The front diff does NOT use 8.5/8.6 gears. It uses 7.6 gears.

The 7.6 was used in many light duty GM rear wheel drive cars & trucks from the mid 70s on. The H3 front diff uses this same gearset flipped around and spinning backwards. The rest of the axle however is special to the H3. Make sure you use “7.6 IFS” when referencing parts.

www.demandaam.com

 

[JPaul]

The front diff does NOT use 8.5/8.6 gears. It uses 7.6 gears.

The 7.6 was used in many light duty GM rear wheel drive cars & trucks from the mid 70s on. The H3 front diff uses this same gearset flipped around and spinning backwards. The rest of the axle however is special to the H3. Make sure you use “7.6 IFS” when referencing parts.

www.demandaam.com

Derp. You're right of course, I was thinking the rear gears. That's what happens when I have to work almost 60 hours plus spend until 2am Saturday working on my truck.

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[FloridaH3]

Thanks guys.

I haven’t rebuilt diffs before so will likely take it to a shop to quote a rebuild. I do love learning and knowing what is inside my vehicle, what the moving parts look like and research for future reference when I may be able to do it myself. So thanks for the advice and the pdf reference!


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[FloridaH3]

Stupid question but out of curiosity, does dropping the front differential and taking out the cv axles do anything detrimental other than disallowing 4x4?

Need to drive my truck intermittently, but would like to not keep grinding the diff away if possible. Thoughts? (Don’t have money to fix diff for a month or so)


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[JPaul]

No, I had to run mine like that most of last year. Put it in 4hi lock or it won't go anywhere, it will stay in that mode until you change it so you don't have to worry about it changing when you stop/start the truck.

However what I did was take a couple of the spare axles I had that seemed to be bad and pulled them apart to get the outer portion so that I could keep everything tightened up in the hubs. Since they are unit bearings I think you can probably get away without doing that, but it's better to err on the side of caution. If you don't have any spare axles (I'd loan you my stubs if you were closer) then you could go get some similar sized bolts, washers, and nuts and use those to apply the clamping pressure. I feel there is a reason GM spec's 191 lbs/ft torque on the stub axle nut, and it's probably not just to keep the axle itself in place.

 

[FloridaH3]

Couldn’t I just use the outer portions from mine? I’m going to fully rebuild the differential when I save the money, so could just pull the outer portions once I uninstall it and put them back in. Just wanting to make sure like you said I take care of buttoning you whatever needs to be buttoned up it’s “normal” and I’m not doing any harm


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[JPaul]

The outers will be ruined by rust, only use sacrificial axles for that.

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[FloridaH3]

Hahaha gotcha, I’ll go swing by the pick and pull this weekend! Thanks so much man.


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[JPaul]

The ones I used might have been rebuildable, but they were wicked stiff so it seemed like they were not in great shape. I also had several others on hand as well, plus they were all free, so it wasn't a big deal for me. If you are planning on reusing your current axles then just get a couple bolts to use instead. It's cheaper than new axles and less work.

 

[FloridaH3]

Honestly the truck is at 222k. Probably might as well replace the axles when I replace the diff, so will just reattach my outer portions to the hub assembly once I drop and install everything.


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[JPaul]

If you're going with new axles then I would suggest the AC Delco's. Not cheap but according to most on here they last a lot longer than the cheaper ones. I just picked up a pair for $220 or so a piece on Amazon.

 

[SlcHummer]

If you're going with new axles then I would suggest the AC Delco's. Not cheap but according to most on here they last a lot longer than the cheaper ones. I just picked up a pair for $220 or so a piece on Amazon.

^^^ what he said. I have a brand new POS cardone cv axle sitting in storage because when I installed it there was a noticeable vibration in my pedals when accelerating. Unfortunately too much time had passed for me to return the POS so now I take it with me to Moab in case I need a spare.

 

[amrg]

Do you guys think the ac delco axles for a chevy colorado will fit on the H3? They run almost $115 cheaper on rockauto (150 vs 265) and I know that the really expensive GMPP upgraded extendable halfshafts for the colorado zr2 do fit on the H3


H3 shafts:

https://www.rockauto.com/en/catalog/hummer,2009,h3,5.3l+v8,1442832,drivetrain,cv+axle,2288

Colorado shafts:

https://www.rockauto.com/en/catalog/chevrolet,2019,colorado,3.6l+v6,3442694,drivetrain,cv+axle,2288


Video showing how the GMPP zr2 shafts fit on the H3

https://youtu.be/wEsu1RVMwdM

 

[JPaul]

Good heck, $3,700 for a pair of axles?? Almost halfway to a SAS with that I think.

Interesting thought though with the stock ZR2 axles. Need some measurements to be sure.

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