Replacing open diff in '00 Silverado

[that1nerd]

I have a '00 Silverado short bed with the 4.3L v6, 4L60E trans, 3.42 open diff. She's currently sitting at 244k miles and still going strong! Sure, I know she's a rather modestly spec'd truck with a ton of mileage, but she was my late father's work truck and has been in the family since new. She's still solid with only minor surface rust in spots, and still gets 18 MPG on the highway. I'd rather keep her on the road than get another truck.

So here's my dilemma. Although the 3.42 gearing is enough grunt for what I need to do, striking a good balance between low-end torque and decent highway mileage, I'm very leery of driving anywhere off road due to the open diff. Since I live in the Tampa Bay area, it's super common for the ground to turn soupy and muddy with only mere hours of heavy rain. I've honestly lost track of how many times I've been stuck in the mud at various job sites and dirt roads over the years, especially in my own back yard, so I'm wanting to swap the open diff for a limited slip or locker to mitigate that issue.

 

Ideally, I'm looking for a diff that is well mannered on the highway and requires as little maintenance as possible. I'm not afraid of doing a DIY install, but would prefer a straight bolt-in option over something that requires a ton of modification and fabrication. I was originally looking into a factory G80 Gov Lock diff, as it sounds exactly like what I want on paper, but I quickly learned of the notoriety around those. Then I got lost in the aftermarket options out there. I'm really iffy about the China knock-off Eaton style units on eBay, and a Yukon Dura Grip has the clutch packs that wear out over time.

Any input here would be greatly appreciated!

[swathdiver]

32 minutes ago, that1nerd said:

I have a '00 Silverado short bed with the 4.3L v6, 4L60E trans, 3.42 open diff. She's currently sitting at 244k miles and still going strong! Sure, I know she's a rather modestly spec'd truck with a ton of mileage, but she was my late father's work truck and has been in the family since new. She's still solid with only minor surface rust in spots, and still gets 18 MPG on the highway. I'd rather keep her on the road than get another truck.

So here's my dilemma. Although the 3.42 gearing is enough grunt for what I need to do, striking a good balance between low-end torque and decent highway mileage, I'm very leery of driving anywhere off road due to the open diff. Since I live in the Tampa Bay area, it's super common for the ground to turn soupy and muddy with only mere hours of heavy rain. I've honestly lost track of how many times I've been stuck in the mud at various job sites and dirt roads over the years, especially in my own back yard, so I'm wanting to swap the open diff for a limited slip or locker to mitigate that issue.

 

Ideally, I'm looking for a diff that is well mannered on the highway and requires as little maintenance as possible. I'm not afraid of doing a DIY install, but would prefer a straight bolt-in option over something that requires a ton of modification and fabrication. I was originally looking into a factory G80 Gov Lock diff, as it sounds exactly like what I want on paper, but I quickly learned of the notoriety around those. Then I got lost in the aftermarket options out there. I'm really iffy about the China knock-off Eaton style units on eBay, and a Yukon Dura Grip has the clutch packs that wear out over time.

Any input here would be greatly appreciated!

Go to LKQ online and look for an entire axle with the G80.  They only blow up when you do donuts and burnouts in them constantly.  Stick with your generation to keep it plug and play.

[that1nerd]

Hah! All the Gov-Lock naysayers I came across were all guys with lift kits and knobby 33s on their trucks, now that I recall. A far cry from a bone stock 4.3 work truck like mine!

Thankfully there's a ton of GM-T800s sitting at the LKQ over in Clearwater, so I'll definitely give that a shot. Only challenge would be finding a G80 truck with 3.42 gears. A lot of them are either 3.08s or 3.73s.

If it came down to it, I suppose I could just reuse the gear and pinyon in my diff and just buy a whole axle as a donor.

Edit: Just looked online at LKQ, and they want over $700 for a whole axle. That and they don't specify if they have the G80 option.

Edited December 6, 2021 by that1nerd
Added an update

[richard wysong]

not sure if you can still get them but a Detroit Locker is an easy install. lts a ratchet mechanism that replaces the spider gears. bullet proof! u do get a driveshaft clang on tight corners when it disengages. I had a 72 k20 with them front and back but had to take the front 1 out because you couldnt steer it in the snow

[that1nerd]

Used G80 axles were a no-go after some more research. The clutch packs in the G80s wear out after 20k miles and become open diffs with clutch material in the oil. Exactly what I'm trying to avoid. All the used ones I found had 100k+ miles on them, were way rustier than the axle in my truck, and the junkyards wanted $300-$500 for the axle plus freight shipping. That's not factoring refurbishing costs.

Ended up buying an Eaton Detroit Truetrac (913A481) limited slip last night, along with AC Delco seals, replacement bearings, and Lucas 80w90 gear oil for about $650 off of Amazon. What sold me was the helical torsen gears in it, so it has the functionality of a limited slip without any clutch packs to worry about. Plus, I get the diff I wanted with fresh oil, bearings and seals for cheaper than a used G80 axle. A no-brainer in my opinion!

As Eaton themselves mention, that diff require different case bearings than stock for the GM 8.6" 10 bolt 30 spline axles like what I have.
Bearing# LM603049
Race# LM603012

I'll report back when I have it installed with some break-in miles on it.

[richard wysong]

sounds like a wise choice

[swathdiver]

14 hours ago, that1nerd said:

Hah! All the Gov-Lock naysayers I came across were all guys with lift kits and knobby 33s on their trucks, now that I recall. A far cry from a bone stock 4.3 work truck like mine!

Thankfully there's a ton of GM-T800s sitting at the LKQ over in Clearwater, so I'll definitely give that a shot. Only challenge would be finding a G80 truck with 3.42 gears. A lot of them are either 3.08s or 3.73s.

If it came down to it, I suppose I could just reuse the gear and pinyon in my diff and just buy a whole axle as a donor.

Edit: Just looked online at LKQ, and they want over $700 for a whole axle. That and they don't specify if they have the G80 option.

 

Wow, they got mighty proud of them, I bought a 14-bolt for about $300 earlier this year with 3.42s in Fort Myers.

 

I just looked, found one with 3.23 gears for $433 and some 3.73s and 3.42s and even 4.10s in 9.5" 14-bolts when changed the year to 2006 and used GMC Sierra.  I know for my generation, all of the GMC trucks have the G80, not sure about yours.

[swathdiver]

1 hour ago, that1nerd said:

Used G80 axles were a no-go after some more research. The clutch packs in the G80s wear out after 20k miles and become open diffs with clutch material in the oil. Exactly what I'm trying to avoid. All the used ones I found had 100k+ miles on them, were way rustier than the axle in my truck, and the junkyards wanted $300-$500 for the axle plus freight shipping. That's not factoring refurbishing costs.

Ended up buying an Eaton Detroit Truetrac (913A481) limited slip last night, along with AC Delco seals, replacement bearings, and Lucas 80w90 gear oil for about $650 off of Amazon. What sold me was the helical torsen gears in it, so it has the functionality of a limited slip without any clutch packs to worry about. Plus, I get the diff I wanted with fresh oil, bearings and seals for cheaper than a used G80 axle. A no-brainer in my opinion!

As Eaton themselves mention, that diff require different case bearings than stock for the GM 8.6" 10 bolt 30 spline axles like what I have.
Bearing# LM603049
Race# LM603012

I'll report back when I have it installed with some break-in miles on it.

Missed this post!  I've got 166K on my stock truck and 110K on my lifted Sierra and the locker works just fine in both.  Even did a burnout a few weeks ago at the drag strip.

 

You'll like that new Truetrac.

[BlaineBug]

The G80 doesn't use clutch packs.  

 

[that1nerd]

3 hours ago, richard wysong said:

sounds like a wise choice

Glad you think so! Thanks for the input.
 

1 hour ago, swathdiver said:

Wow, they got mighty proud of them, I bought a 14-bolt for about $300 earlier this year with 3.42s in Fort Myers.

 

I just looked, found one with 3.23 gears for $433 and some 3.73s and 3.42s and even 4.10s in 9.5" 14-bolts when changed the year to 2006 and used GMC Sierra.  I know for my generation, all of the GMC trucks have the G80, not sure about yours.

Yeah, I guess that there are still a ton of 1/2 ton trucks on the road, thus there being more demand for the 10 bolt rear axles. The more beefy 14 bolts seem to be more readily available and plentiful, ironically. I'd consider using a 14 bolt if I was wanting to do an LS swap in my truck, but at that point I'd just buy a 2500 with a 6.0 or Duramax in it. I learned very quickly how involved of a job it would be to do an LS swap in a v6 truck 1/2 ton truck, let alone drivetrain swaps.

So I heard, for the 1500s with the 10 bolt, they didn't offer the G80 option as standard until the 2002 model year, and my truck definitely predates that. At least I won't have to worry about excessively worn pinyon/ring gears in my diff due to the clutch material floating around in the oil. She has 244k miles and yet the pinyon is still tight. No noise, either. This truck saw a ton of highway miles, so oil was definitely circulating around in there. The seal is leaking, though, so I plan on replacing it while I'm in there.

 

1 hour ago, swathdiver said:

Missed this post!  I've got 166K on my stock truck and 110K on my lifted Sierra and the locker works just fine in both.  Even did a burnout a few weeks ago at the drag strip.

 

You'll like that new Truetrac.

Nice! A good locker makes a huge difference with these trucks. I'm partial to the limited slip because I intend to keep using my truck for work. (Clearing brush and trash, moving furniture and appliances, hauling building materials, towing the occasional trailer, etc.)

The parts are scheduled to be dropped off this Thursday, so I'm looking forward to getting greasy this weekend.

[that1nerd]

1 minute ago, BlaineBug said:

The G80 doesn't use clutch packs.  

 

Maybe for the GM-T900s they had factory lockers. All the factory 10 bolt G80 diffs I kept finding for my truck were the traditional clutch type limited slips. Guess I was referencing the wrong part number?

[BlaineBug]

1 minute ago, that1nerd said:

Maybe for the GM-T900s they had factory lockers. All the factory 10 bolt G80 diffs I kept finding for my truck were the traditional clutch type limited slips. Guess I was referencing the wrong part number?

I don't know, but if it was a different design using friction discs I would think it would use a different designation than G80.

[BlaineBug]

Now that I look into it, it appears all of the G80s have clutch packs.

[that1nerd]

1 minute ago, BlaineBug said:

Now that I look into it, it appears all of the G80s have clutch packs.

Heh. That's the confusing part about GM and their RPO codes. They reuse the same code for different parts, across different year ranges, and even between different makes and models. There's a G80 code for the Camaros, for example.

I found out about the clutch packs in the G80s when I found mrboss429r's listing on eBay. (He specializes in rebuilding limited slip diffs.) The listing mentioned that the clutch pack was replaced, which clued me in.

[BlaineBug]

I apologize.  I was formerly under the assumption that it was a "maintenance free" locking differential.  It also does NOT need limited slip additive.  I know that part for certain at least.