2500HD Rear Axle

bigdogs · September 9, 2003

Hi, I am new here and just bought a 2003 Sierra 2500HD truck with the Duramax/Allison combo. I do have one question (well atleast right now). Does anyone know if the rear end on this is a full floater of semi floater? I did read that it has the 11.5" rear end (looks like a Dana cover to me, not like the old 14 bolt ones) and did come with the G80 3.73 posi code. I do remember from years ago, they would put the same full floater 14 bolt on the 3/4 pickups and suburbans that they did on the 1 ton models, but I'm not sure about this one (and didn't want to take the tire off just to see if there was a hub there or not. So if anyone has that info I'd be grateful for the answer

Thanks

westex39 · September 9, 2003

Yours is a full floating type rearend. I have the 2500HD with a 6.0L and a 4L80E transmission. It has a 10.5" ring gear and it is a full floating type also. The easiest way to tell is to look at the end of the axle shaft where the wheel mounts. If there is a flange on the end of the axle shaft with 6 bolts in it, it is a full floating type.

regards

Westex

hdmax · September 9, 2003

Hi, I am new here and just bought a 2003 Sierra 2500HD truck with the Duramax/Allison combo. I do have one question (well atleast right now). Does anyone know if the rear end on this is a full floater of semi floater? I did read that it has the 11.5" rear end (looks like a Dana cover to me, not like the old 14 bolt ones) and did come with the G80 3.73 posi code. I do remember from years ago, they would put the same full floater 14 bolt on the 3/4 pickups and suburbans that they did on the 1 ton models, but I'm not sure about this one (and didn't want to take the tire off just to see if there was a hub there or not. So if anyone has that info I'd be grateful for the answer

Thanks

Yes it is the full floating 11.5" rear differential. It is not the Dana, it is an Ameracan axle. The duramax comes with only the 3.73:1 axle ratio and it come with or without the G80 option. You will have to check the list of options to see if you have it. The 11.5" rear end is in the 8.1L option but has 3.73:1 or 4.10:1.

The hub will tell you that the axle is a full floater.

bigdogs · September 9, 2003

Thanks I had "thought" (well atleast hoped) it was a full floater but had not taken off the wheel yet to see if it had a hub and unfortunately with the rims that are on it, you need to take it off to see the center. All I could get out of the dealer was they thought it was a semi but were not sure, but it seemed to surprise them I asked in the first place and they didn't seem equipted to answer it.

I'm not familar with the American axles, just the Dana and the 12 and 14 bolt corporates axles from when I did a conversion on an '80 Blazer to 1 ton running gear. I really did like how well the 10.5" unit was put together so hope this 11.5" one is put together as well.

I know from the codes it has the G80 posi and according to the options list it was the 3.73 which seems all that comes with the Duramax.

CMNTMXR81 · September 9, 2003

American Axle and Manufacturing has been supplying GM for years. Driveshafts (including at least the front ones on all GM 4x4 systems), rear ends, pumpkin mounts, etc, etc are all supplied by AA&M.

bigdogs · September 9, 2003

I did not know there were supplying the rear axles and more for GM for that long. Did the make the 14 bolt corporates as well?

I assume they also make the posi for this rear end as well. I hope it is not a "gov lock" like they had on the 14 bolts when I had one as they could be kinda weird in locking up.

Do they also make the front diff as well? With the IFS it is hard to tell even how big of a unit is up there, since I'm more used to the straight axle fronts.

Thanks again to all for reassuring me it is a full floater w/o having to take the wheel off as all I could get out of the dealership was that it was they think it is a semi-floater.

Colorado Kid · September 9, 2003

I did not know there were supplying the rear axles and more for GM for that long. Did the make the 14 bolt corporates as well?

I assume they also make the posi for this rear end as well. I hope it is not a "gov lock" like they had on the 14 bolts when I had one as they could be kinda weird in locking up.

Do they also make the front diff as well? With the IFS it is hard to tell even how big of a unit is up there, since I'm more used to the straight axle fronts.

Thanks again to all for reassuring me it is a full floater w/o having to take the wheel off as all I could get out of the dealership was that it was they think it is a semi-floater.

Yup, American Axle spun of from GM a while back. All the "Corporate" axels are now AAM (American Axle Manufacturing).

The D-max uses an AAM 9.25" front diff, the same center section from the 9.25" 14 bolt semi-floater.

Um, , well, the G-80 is Gov-lock, but the good news is I haven't heard of anyone grenading the 11.5" version.

--Let me clarify that, I've heard of folks not giving the massive rear end a gentle break in, who destroyed it by overheating it. But I haven't heard of any failures attributed to the locker.--

You'd hope that someone at the dealer at least knew that much about a drivetrain that they've been selling for three years.

bigdogs · September 10, 2003

I heard the name American Axle awhile ago when looking at a Dodge truck but never heard of them before that and didn't really pay much attention to it afterwards.

Thanks for all the info on the different diffs this 2500HD has. I'm glad it does have the full floater and the dealer was wrong,

As for the gov lock posi, The one I had was an Eaton and in all honesty who knows how old as bought it out of the paper when converting a Blazer to 1ton running gear so it could have just been "odd" It worked fine just didnt like how it took that much slip to get it to lock both axles. The power lok in front acted much better IMO. I sure like how it has discs instead of those 5 gal pail sized drums the old 14 bolt had, atleast now you can check the brakes w/o getting a hernia

Does anyone make a posi for the front end of these units?

jbplock · September 10, 2003

Isn't the G80 option for the 2500HD/3500HD an Eaton Locker ??

bigdogs · September 10, 2003

Dunno... from the code definition I saw, it just said HD locking rear differential.

revrnd · September 10, 2003

When I change the gear lube in my truck, I'll check the diff in my truck. It has the G80. It would be nice if it wasn't the Gov-loc in there.

awdvkd · September 10, 2003

yes they are eaton lockers

Colorado Kid · September 10, 2003

Eaton Locker,

Gov-Lock,

GM Locking rear Differential are all names for the same thing.

The good news is that, according to Eaton's site, the Gov-Lock locks with lower wheelspeed differences than it used to.

I believe that the Eaton E-locker has been adapted to the front diff of at least one D-max.

bigdogs · September 11, 2003

Well that is good to hear they improved it. I ended up replacing my gov lock in the 10.5" with a detroit locker to more match the power lok in the Dana 60 in the front.

One nice feature the old (maybe newer ones too??) 10.5" corporates had was the pinion bearing for the "nose" of the pinion gear.