8.6 because of 18's?????

[DustinC1989]

So since I got my 8.6 yesterday, while I was at work I was looking up the bearings and stuff to order. I looked up axle shafts just for giggles and Napa shows there are part numbers for the I-6 and V-8... But they also list an option for I-6 with 18" rims and the part numbers are the same as the V-8

So what that makes it look like is factory 18" rims also got the 8.6? Anyone know any truth to this? I honestly didn't even pay attention when I changed the diff fluid and my fiancée has the trailblazer out of town so I can't go visually verify.

[mikekey]

They're system could be confusing the Trailblazer SS, but those axles don't match up. The SS has a larger rearend. Sometimes AutoZone, Napa and those places have the wrong information listed.

I've been given the wrong part they said their system said was correct more than once.

[DustinC1989]

That's what I thought since I had to buy and return 6 sets of bearings for the 8.8 I rebuilt last month. But Napa, autozone and Car Quest, all had it listed that way so I figured maybe it was possible, GM has done some weird stuff in the past. She should be home in about 2 hours then I can verify

[DustinC1989]

Hard to tell with all the crap in the way and since they both look somewhat alike. Guess I'll drop the spare tomorrow and look closer because from the little bit I can see.. It looks the same

[DustinC1989]

Bringing my own thread back since I completely forgot about it....

But I just read in exb5182's build thread that he got a 8.6 out of an 08 4.2 w/18" rims, so i went out to check before I forgot again... 2 jobs and planning a wedding does that

18" rims does INFACT give you a 8.6
so I have a 8.6 in the truck already and the 8.6 I've been rebuilding that I bought to replace the "8.0"

[TBYODA]

So how are determine this just by going by the rim size or did you measure the ring gear? I just don't understand how bigger wheels coming to play in the bigger size of the axle. I am curious cause I have stock 17" and 08 4.2 wondering if in fact I got a 8.6 but I am thinking this a stretch.

[DustinC1989]

30 spline axles, 8.6 stamped on the cover and same exact cover as my 8.6 in my shop.

Looked under my buddies trailblazer (only difference from mine is color) also has 8.6 stamped on the cover, though I wasn't able to pull an axle to count splines

[KingBird]

I would think that it would have something to do with needing more strength to handle a heavier rotational mass or whatever. I'm sure an actual engineer could explain it.

[DustinC1989]

I don't think there are very many people with the 18" factory rims on here, starting a thread on GMT shortly to see if any others can help confirm this 100%. So far there are 3 06+ LT's with the 18's that have all had the 8.6.

[HARDTRAILZ]

Interesting find.

[Chango]

So what you're saying is..you have an extra 8.6?? Humm

[DustinC1989]

What I'm saying is, 8.6's are a little more common than previously known.

Also, yeah, there's a spare axle in my shop.

[DustinC1989]

One of the local ham's I know has a 08 LT w/18's, has 8.6 stamped on his cover as well. He wouldn't let me open it up to verify spline count and measure though.

Would like to verify a couple more if I can find them.
But it looks like people with factory 18's don't have to upgrade and people looking to upgrade have another option to pull from

[HARDTRAILZ]

Damn Dustin... you know more TBs w stock 18s than I have ever seen. I thought the 18s were a rare option you had special order.

[DustinC1989]

We're every place, our different grill just helps us blend in

Actually, I see them all the time, don't think climbing under random Trailblazers in the Meijer parking lot would go over very well though.
With mine, my buddies and the local ham, that's 3. exb5182 pulled his out of a TB with the factory 18's, which brings us up to 4 with 18's that have all had a 8.6.

No hits on GMT yet, but it helps find info people could benefit from so I'd like to confirm they all had the 8.6 from the factory

[HARDTRAILZ]

I have literally known of one member of either forum other than you that had factory 18s.

[DustinC1989]

Apparently they shipped them all to Calhoun county, Michigan... I see them constantly, thought they were common
Well when they are found, their axles can be used...

[HARDTRAILZ]

Trailblazers it seems rare, but were 18s standard on Envoy Denali's? I thought I recalled them having bigger wheels, but most had v8. I think Fletch has 18s on his white TB, but he may have bought them from dealer since I know he runs two sets of wheels.

That is crazy that you see so many with 18s. Are they LT generally?

[DustinC1989]

Yeah, they are part of the LT/LS package (the 06+ LTZ).

We have another member on here with them, but I don't remember who it was and I don't believe they are very active anyway.
I know the Denali's have 18's, but as far as I know they have the 5.3.

I wonder if Rob (tbyoda) has had a chance to look at his axle with the 17's, maybe the basic LT's got the 8.6 because of the different bumpers and grill lol

[TBYODA]

I wonder if Rob (tbyoda) has had a chance to look at his axle with the 17's, maybe the basic LT's got the 8.6 because of the different bumpers and grill lol

That would be nice but I doubt it. I don't see any 8.6 stamped on the cover. Just this. Stilly me never even thought to measure the ring gear when I had the cover off last summer when I changed the fluid.