what rear axle 2002 250HD

[chris989]

Hello all,

Potential dumb question alert.

While at the junkyard scoring fenders for my square body there was an HD2500 next to me. The rear axle was 70 removed and just waiting for me to take it home.

It has disk brakes and I glanced under it assuming it was a 14 bolt. Did this year come with the 10.5" 14 bolt or the 11.5 AAM??

After some research I am getting all different answers of what year the 11.5 began in the 2500 trucks. Rock auto list a multitude of covers and gaskets (9.5-11.5) so that is no help. Some internet info say it changed in 2001, some say it did not?????

Trying to save a trip back if it is the 11.5. That is overkill for my suburban.

Thanks,
Chris

[hatzie]

Both were possible depending on the engine option.
Both were made by AAM and both are good axles.
I wouldn't hesitate to use either one.

The LB7 Dirtymax and L18 8.1L equipped pickup trucks got the 11.5 and the Allison transmission.
The LQ4 6.0L pickups and the 2500 Suburbans got the 10.5 and the 4L80E.

In a 2500 they'll both have 8 lug hubs.
Look at the SPID sticker in the glovebox for the axle ratio RPO code.
G80 was limited slip in these years not the Eaton Gov Bomb IIRC.

You can tell right away which AAM 14bolt full floating axle it is by looking at the pinion support housing.
The 10.5" AAM Pinion Support is bolted in just like the GM corporate 14bolt it evolved from.
The 11.5" doesn't have a bolt in pinon housing.

[chris989]

Hatzie,

Thanks for the reply, I was searching for info when i got your message.

My wife's 2002 2500 burb 6.0 has the 10.5 ff aam. I am going back to the JY now and try to get it. I really only want it for the factory disk and if it is 411 gears I would like to come down from the 456s i run now.

I believe they are metric studs in that year but still 8x6.5????

Thanks,
Chris

[hatzie]

8 on 6.5" (165ish mm) til 2009. 2010 is a changeover year so not sure what you'll find. 2011 and newer is definitely 8 on 180mm.

They are metric studs. Scoop up the lug nuts from the front wheels if they're around. I try to put stuff like that inside the vehicle and not bust stuff up so the next guy has a chance of finding the parts if they need them. No need to smash up stuff or drop on the ground things that someone else might need.

Axle ratio RPO codes... https://www.crawlpedia.com/rpo_axle_codes.htm

[chris989]

It has part number 40002779 on the axle housing. That should be a corporate 14-bolt and not an aam.

Everything says this shouldn't be the 14 bolt but it sure looks like it

[hatzie]

AAM built the 10.5 and 11.5 for GM and Dodge.
If it's manufactured as a GM axle it's the same as the older corporate axles except it's setup for factory disc brakes with full on drum & shoe parking brakes inside the rotor hats and the leaf spring perches are setup for the T800 frames. The cover is held on by 8mm bolts rather than the SAE bolts used on the older drum brake axles but that's small fry in comparison to the factory disc brake setup.

The Dodge axle has several differences from the GM part so they aren't interchangeable.

GM outsourced solid axle manufacturing to AAM. It's still the good old GM design with some modernization.
It's just like Dana axles, Saginaw steering boxes, and New-Process/New-Venture transfer cases and transmissions. Everyone uses them with their own special differences to fit their vehicles.

[chris989]

Therein lies my problem.

While reading some internet forums I thought the AAM was was a different axle. The post must have been talking about the Ford/dodge axles compared to GM.

I currently run a 9.5 SF with 4.56 gears,, It is in a small block suburban with 35s and does well. It is not a crawler or high HP build. I had a 14bolt before and decided not to use it due to ground clearance. I was considering the new axle for the disk brakes.


Thanks for the help.
Chris

[hatzie]

Originally Posted by chris989

Therein lies my problem.

While reading some internet forums I thought the AAM was was a different axle. The post must have been talking about the Ford/dodge axles compared to GM.

I currently run a 9.5 SF with 4.56 gears,, It is in a small block suburban with 35s and does well. It is not a crawler or high HP build. I had a 14bolt before and decided not to use it due to ground clearance. I was considering the new axle for the disk brakes.


Thanks for the help.
Chris

Eventually the 9.5 Semi-Foating will probably force the issue. They aren't noted for longevity and 35" tires will not help even if you just drive it.
The difference is the outer axle bearings. The SINGLE 9.5" bearing is noticeably smaller than the full floating pair of taper roller hub bearings. The 9.5" diff bearings are somewhat smaller as well but that's not as big a deal as the single bearing hub end.
The difference between a single parallel roller bearing that's transferring some of the load to the diff and C-Clip and the pair of much larger taper roller bearings riding on the outside of the full floating axle bolted to the hub is the full floating hub and the big axle tube take up all of the side load from the tires with no load being transferred to the diff along the big fulcrum called a semi floating axle. This is what makes the 10.5 & 11.5 so much tougher.
The differential itself isn't the problem. If GM had made the 9.5 full floating with two taper roller bearings riding on the outside of the axle tube inside a hub it would easily put up with 35" tires.


IIRC the 9.5 & 10.5 14bolt center castings are similar in size. It's been a while since I had a 9.5 to look at tho.

I can't see where the 9.5 would have significantly more ground clearance than the 10.5" axle. I would think that the 35" tires would make a larger difference in ground clearance than going to a 1" larger 14bolt axle.
The pinion and diff bearings are larger but those are on the center-line of the axle. 1" larger ring gear diameter is 1/2" larger on the radius... this means the OD of the ring gear is only 1/2" further from the center-line of the axles at any given point around the circumference. That might or might not translate to a larger housing.
The contact face of the pinion gear is larger but that's from the center-line of the axle again so it won't affect ground clearance.
The larger axles do also have larger pinion yokes so you'll need to mod your propshaft to mate with it. Either a hybrid Universal joint or cut and weld a new larger yoke onto the shaft or get a propshaft from a full floating truck.

This is a semi floater compared to a big truck full floater with a bolt in spindle rather than a machined axle tube but it does graphically show the difference.

[chris989]

Hatzie,
Thanks for replying,

I agree the SF is not the best. I build classic and the first thing we do to 12 bolts is cut the axle tube ends off and use Ford big bearings to eliminate the c-clips.

When i did this build many years ago i was thinking more about HP loss and ground clearance. I guess I will grab the 14 bolt on monday. It is only 200$ and everything looks like new.