GMT800 Suburban Differentials?

[FourOff]

I have a 2003 Suburban LS with 230K miles that I'm planning a big driveline overhaul on. Engine has a saggy lifter and needs a few fixes (like the knock sensors), so I'm going to buy a junkyard motor and rebuild it, limiting the truck's downtime. With that, I plan to get the transmission rebuilt and I'd like to get the differentials rebuilt and/or upgraded as well. This is where my vehicle expertise is limited and need some advice from y'all. I've noticed some unnecessary tire spin when I take this off-angle right turn near my house, so I think I need a better (or fixed?) limited slip in the back. I'd also like to get some lockers while I'm in there.

I know the Z71 had factory lockers and different gearing. Is it worth yanking these (and the necessary wiring) from a junkyard? This isn't my favorite option, as yards around here seem to be pretty limited.
Or would it be better to go aftermarket with lockers and LSDs?
Or a combination of better parts from another truck and aftermarket?

For additional context, I'm on 33s with a "light" lift (keys and HD rear springs + Bilstein 5100s), so I don't need a serious gearing change (especially since 95% of the time I'm highway/street cruising).
Appreciate any insights/experience/knowledge you might have here.

 

[djp73]

There weren't any factory electric lockers offered. Just the G80 Gov lock, you might already have it. Check your RPO sheet.

 

[FourOff]

There weren't any factory electric lockers offered. Just the G80 Gov lock, you might already have it. Check your RPO sheet.

Sadly, no.

 

[SubSar]

Any Suburban/Tahoe/Yukon GMT800 with the factory tow package should have the G80 locker. I have an ‘03 Suburban LT with the tow package, 3.73’s and the G80 on 33’s. It cruises just fine around town and on the highway.

 

[XJLI]

The 6 lug 14SF bolt (9.5") bolts right up. Those all have 3.42s and the G80. Look for a 07-14 6.2 powered Escalade or Yukon Denali. I think it may have only been the 2WD trucks too, but I'm not sure. You'll know when you get under them. You'll need to swap the yoke from your 10 bolt or use a 3R to 1350 conversion ujoint.

If you really want to keep junkyard hunting, you can use the H2's factory e-locker in that axle. But not the whole axle, since its different width and mounting than the Tahoe/Burb and 8 lug as well. You need the wiring harness and some bracket and all that. Eaton made the lockers. Probably easier to just put a Detroit in it.

The front end is your weak point after that, mainly CVs and the aluminum housing. Don't upgrade the CVs, because now your fuse is the diff housing. There have been people who have successfully swapped the iron 2500 front diff in and converted to 8 lug. Then you have to match the back now too. Then you still have a 4L60. Easier to just buy a 2500 in the first place.

At the end of the day, the G80 is the weak point of the 8.6. Upgrading the ratios F&R to 4.10, and putting a full case like an Eaton E-locker or ARB on 33s will give you extra gear for the heavier tires and enough confidence to blow up front CVs (instead of your rear axle) on the trail.

 

[FourOff]

Easier to just buy a 2500 in the first place.

Exactly. I'm not doing any "serious" trail work. Mostly looking to bring the driveline at least back to "new" and then some "light" upgrades where practical. A rebuild, gear change, and e-locker looks to be the "easier" way to go. Appreciate the insight.

Anybody have experience with any of the aftermarket e-lockers? Do I "need" (or is there a lot of value in) front and rear?

 

[XJLI]

Anybody have experience with any of the aftermarket e-lockers? Do I "need" (or is there a lot of value in) front and rear?

I found the G80 to be fine for mild stuff, it does the job. There's nothing available from the front diff.

 

[FourOff]

Thanks for the advice, gang.
Found a G80 for the 8.6 / 30 spline rear with 3.73 gears, so have that coming. Now I just need to find a good shop nearby to put it in. Shimming a diff is something I'll leave to a professional.

 

[djp73]

Get a whole rear end and swap it yourself.

 

[FourOff]

Update: Buying a Z71, like I should have done in the first place
At least now I have a spare G80 for it...

 

[1stDeuce]

On GMT800, Z71 didn't get you anything worth holding out for... Shocks, skid plates, and possibly the rear G80 standard, but that's about it. Shocks have likely been replaced anyway, skid plates are about worthless on GMT800's, and you already had the G80 coming...

If your truck doesn't have 3.73's, and the new one does, that will be nice I suppose. 4:10's would be better for 33's, but the're really hard to find on the half tons...

I ran a lockright in the back of a pickup with the old 12 bolt rear axle. It was OK, but pretty annoying on the street. ALL my trucks now have G80's in them, and they work fine for high range wheeling and that offroading that I do. In low range, it takes more wheel slip to lock them in than you will want to get when going slow, but a little parking brake action tends to bind them up some, and if that doesn't work, I row up into 2-high, get the diff to lock, then go back to 4-low and that gets me through.

As stated, there is nothing for the front, but Suburbans are so heavy that lockers don't often come into play unless you're lifting tires off the ground...

Good luck!!!

 

[FourOff]

On GMT800, Z71 didn't get you anything worth holding out for... Shocks, skid plates, and possibly the rear G80 standard, but that's about it. Shocks have likely been replaced anyway, skid plates are about worthless on GMT800's, and you already had the G80 coming...

If your truck doesn't have 3.73's, and the new one does, that will be nice I suppose. 4:10's would be better for 33's, but the're really hard to find on the half tons...

I ran a lockright in the back of a pickup with the old 12 bolt rear axle. It was OK, but pretty annoying on the street. ALL my trucks now have G80's in them, and they work fine for high range wheeling and that offroading that I do. In low range, it takes more wheel slip to lock them in than you will want to get when going slow, but a little parking brake action tends to bind them up some, and if that doesn't work, I row up into 2-high, get the diff to lock, then go back to 4-low and that gets me through.

As stated, there is nothing for the front, but Suburbans are so heavy that lockers don't often come into play unless you're lifting tires off the ground...

Good luck!!!

It was a bunch of reasons it made more sense to grab this Z71 than to keep putting money into the LS. The price was right, and while it needs some love (torn seats, busted bumper, brush rash, etc), it has a lot of things I was missing on the other truck besides the G80 and 3.73s (leather, heated seats, lower miles, a bunch of work done to the motor recently) so it made sense to switch to another truck instead of dumping money into the other one.

Hoping the weather is decent this weekend so I can start swapping parts over!