G80 9.5 rear end

[Supercharged111]

The 14 bolt 11.5" full float only came in the GMT 800/900 trucks with the 8.1 big block and 6.6 TD. I believe all the 2KXX 2500/3500 series are now running the 14 bolt 11.5" axle. I'm sure it's same or nearly the same axle as the Ram 2500/3500 with the 11.5" ring gear.

The GMT 400 3500 HD (GVWR = 15,000 lbs) ran Dana 80 and some Rockwell axle. REALLY heavy stuff. Looks almost like what the semi trucks run.

Dana 80 ring gear was 11.25", so close enough.

 

[96z71sas]

There's 5 rear ends IIRC

The "10-bolt/14-bolt" refers to how many bolts you can count on the diff cover.

8.5" 10 bolt
9.5" 14 bolt 6-lug SF (rare-ish)
9.5" 14 bolt 8-lug SF - yours
10.5" 14 bolt 8-lug FF
10.5" 14 bolt 8-lug FF Dually (idk exactly how this one is different from the other FF 14-bolt but I imagine it is)

Then the other questions are:
What's the ratio: I've seen 3.42s all the way thru 4.10s from the factory. There's some math you can do by counting the teeth or something to figure this out, or RPO codes.
Locker or Open: Either has the g80 RPO code in glove box, or its open.

*All of this assuming its a stock rear*

Thanks for the help I chalked the tire and yoke think it’s 373 but it’s open diff that’s gotta go I found a posi unit on eBay for 250 I’d keep my ring and pinon I can do install but I’m not sure how to measure the backlash I’ve never done it

 

[96z71sas]

RPO code - if you still have it?
Mine is a 14 bolt G80 - I can check the code for you if that helps.

I don’t trust rpo code on this it does say g80 I’m pretty sure it is with 9.5 I wanna do a posi or locker in it I never did one I’m worried about backlash and marking the bearing caps you ever do one?

 

[red98]

Thanks for the help I chalked the tire and yoke think it’s 373 but it’s open diff that’s gotta go I found a posi unit on eBay for 250 I’d keep my ring and pinon I can do install but I’m not sure how to measure the backlash I’ve never done it

I'd skip the stock locker and step up to something made by Eaton, you'll spend a bit more up front but you won't blow out your locker and ruin the entire axle with a posi-trac, true-trac or a Detroit locker, you may with a g80.

Plus the g80 is pretty tame as far as actual lockers go, since it only locks in very specific circumstances (up to 20mph and wheel speed diff has to be pretty high), and is only really useful for taking off in slick conditions. A Detroit locker is max traction at all times unless turning (both wheels physically locked at the same speed by gears, which un-mesh when making turns), but I've heard its a lot less streetable. The posi-trac is ACTUALLY a POSI that uses clutches to keep the wheels locked at the same speed, and lets them slip as needed for cornering, not as strong as the Detroit locker, but also not as harsh. Then there's the true-trac which is like a mix between the two, it uses gears to lock the wheel speeds together but instead of locked all the time, only unlocking for cornering, its unlocked all the time, and only locks for acceleration.

As far as actually doing the work, can't say I've personally been into an axle before, so no clue.

 

[Pinger]

I don’t trust rpo code on this it does say g80 I’m pretty sure it is with 9.5 I wanna do a posi or locker in it I never did one I’m worried about backlash and marking the bearing caps you ever do one?

Nope. Changed the oil and hope I don't have to go inside it.
There are members here who know how to set up a diff.

 

[PlayingWithTBI]

On a 10 bolt, if you get a "lunch box" locker AND you don't have a G80, you don't need to worry about anything. You just remove the spiders and install the locker. On other designs, yes you need to adjust pinion depth and backlash but, it's not all that hard with the proper tools. Here's a .pdf with what you need to do with specs on a 10 bolt. AFAIK It's pretty much the same with a 14 bolt.

 

[96z71sas]

G80 code on the SPID label (option code label in the glovebox) for the Eaton Gov-Loc locker option on these trucks. It ain't posi.. it's a locker. This of course only applies if the rear end hasn't been swapped out. So on to my next points:

Go ahead and pull the cover. You want to know what condition it's in before you buy it, right? Check condition of the teeth, look in the housing for any broken parts, condition of the lube, crap stuck to the magnet, etc.

With the cover off, you can easily identify the Gov-Loc by its crazy appearance of the carrier. You can also confirm the gear ratio at that point by looking for the numbers stamped into the edge of the ring gear. Divide the larger number by the smaller number. 41 by 11 for example would be 3.73's

Richard

Ya I guess your right those teeth got 185000 on Em so I may as well get whole new unit maybe I’ll wait find a full floater with disc brakes on it thanks for help

 

[Supercharged111]

Ya I guess your right those teeth got 185000 on Em so I may as well get whole new unit maybe I’ll wait find a full floater with disc brakes on it thanks for help

I put a used 200k diff in over 80k ago. . .

 

[Schurkey]

IF you keep the ring 'n' pinion, merely transfer the ring from the open carrier to the "posi" carrier, all you have to do is get the backlash EXACTLY THE SAME AS IT WAS ORIGINALLY, while getting the preload correct for the new bearings. At least, I assume you're installing new bearings. The 8.5 axle uses shims for backlash and preload, the 10.5 axle has screw adjustment (no parts to buy), and I can't remember what the 9.5 axle uses.

Once you dick with the pinion, you have to set more adjustments to get things right. More than twice the work.

 

[Erik the Awful]

The "10-bolt/14-bolt" refers to how many bolts you can count on the diff cover.

Careful! This is not always true! It used to refer to the number of bolts on the ring gear, not the diff cover. Lots of older hot rodders got screwed buying "12 bolt" rear ends that had 10-bolt ring gears. The 14-bolt rear ends actually have 14 bolts on the diff cover and 12 on the ring gear, so it holds true in our cases, but just know it's not always a hard and fast rule.