What to do with rear end?

[Schurkey]

There all listed by mileage. Does mileage matter on these?

The ten-bolt I took out had ~300K on it. I wanted it gone in part because it was getting sloppy. Ended up trading it to a friend, who's still using it under his Extended Cab.

The 9.5 SF I put in had ~300K on it. Looked beautiful inside. Doofus prior owner screwed up the brakes pretty bad, and that took a while to sort out. Needed axle seals, too.

Do all the 14 bolts come with a locker?

No. Mine did. The 9.5 Gov-Lock is not as explosive as the 8.5 Gov-Bomb.

Although...the locker doesn't seem to work any more. Maybe because I didn't install the right fluid. Maybe there's a "real" problem. I can't find anything wrong, though. No missing chunks, no pieces fell out.

 

[98chevy2500SS]

I agree with the others on getting the 9.5" 14B SF for 33's. Since you will be running 33's, 4.10s would be my preferred gear ratio. My 97 has 285/75r16s (close to 33's) and the 9.5" 14B SF rear end with 3.73s, it's alright, but wished it had 4.10s. Most of the 6 lug 14B SF rear axles that I have seen came with 3.73s. G80 seems to be common in them as well. I don't think mine works anymore in my 97 lol.

 

[Jrowdy]

Updates!!

Thanks to the tip from dxf2x4 I’ve located a 6 lug 14 bolt 3.73 with the g80 opt. Picking it up tomorrow. Also has f44 option listed. Does that change anything?

Now it sounds like the lockers quit working after a while? What would cause that , and how do you fix that?

Cousin stopped by today and I got to check out the wheels he’s giving me. 20” fuel Mavericks but they’re on 275s and about 80% tread left. With that being said I will be running those till I need new tires but still intend to put 33s on it.
Also holding off on the lift.

Should I still change the gears from 3.73 to 4.10 now , or should I do it when I put bigger tires on it?

Any other recommendations with the tires being 275s now and this rear end swap?

 

[df2x4]

Now it sounds like the lockers quit working after a while? What would cause that , and how do you fix that?

The most common cause of the G80 lockers not working correctly is people putting in the wrong oil. They need GL5 rated 80W-90 and NO friction modifiers or additives. If you put an additive in they won't engage properly. The first thing I always recommend to anyone having G80 troubles is to drain the oil and refill it with the correct stuff.

 

[98chevy2500SS]

Updates!!

Thanks to the tip from dxf2x4 I’ve located a 6 lug 14 bolt 3.73 with the g80 opt. Picking it up tomorrow. Also has f44 option listed. Does that change anything?

Now it sounds like the lockers quit working after a while? What would cause that , and how do you fix that?

Cousin stopped by today and I got to check out the wheels he’s giving me. 20” fuel Mavericks but they’re on 275s and about 80% tread left. With that being said I will be running those till I need new tires but still intend to put 33s on it.
Also holding off on the lift.

Should I still change the gears from 3.73 to 4.10 now , or should I do it when I put bigger tires on it?

Any other recommendations with the tires being 275s now and this rear end swap?

F44 means that the truck has the bigger rear end. It's commonly called the "heavy half" option.

What size of tire are the 275s? 275/60r20? If so, they are essentially the same height as a 33x12.5, but are skinnier. If it were me, I would do the 4.10 swap now, rather than later.

 

[Schurkey]

The most common cause of the G80 lockers not working correctly is people putting in the wrong oil. They need GL5 rated 80W-90 and NO friction modifiers or additives. If you put an additive in they won't engage properly. The first thing I always recommend to anyone having G80 troubles is to drain the oil and refill it with the correct stuff.

Easier said than done.

The GM part number for the "correct" gear lube has been superceded/discontinued. I went nuts trying to find the updated number.

Closest I got was for a fluid that had "for use in passenger car axles" printed on the bottle, essentially a warning to not use it in "truck" axles.

There's a bulletin that GM published warning about using the "correct" fluid in a G80 axle; but I'm not sure the "correct" fluid even exists any more.

In the meantime, every gear lube supplier claims their stuff works great, even though 90% of the part numbers have the "posi additive" in them.

I have a theory about all this, but I'm keeping quiet about it until I get my G80 axle working again. I'd hate to give unproven, unverified advice.

 

[Supercharged111]

GM is still putting gov-bombs in their trucks, right? If so, the spec must be what the new trucks take? I have 4.10 gears in my 1500 with 285/70/17 which is around 33 real inches tall when new and it's a good combo. Way back when I first went to a 33 I had 3.73s and it made the truck a bit of a turd. After a junkyard 4.10 swap my power was restored. And I did reuse u-bolts, but mine were pristine.

 

[CrustyJunker]

Easier said than done.

The GM part number for the "correct" gear lube has been superceded/discontinued. I went nuts trying to find the updated number.

This is probably the stuff you're looking for...GM part # 89021669 :

https://www.summitracing.com/parts/ado-10-4051

The stuff I bought from the dealer I think had the updated "GM VehicleCare," label. It was the same size/shape container.

 

[df2x4]

^ That's it.

@Schurkey you're right about the passenger car axle warning on the bottle but it matches all the necessary specs and has no additives. I can also confirm that it definitely fixed some erratic behavior that was caused by friction modifier.

 

[Schurkey]

Yup. That's the stuff I bought (AC-Delco branding, but with the GM part number 89021669 in addition to the Delco part number 10-4051 printed on the bottle.)

Back side of bottle specifically says "For use in passenger cars only. Not intended for use in trucks".

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