Suburbans: GMT800 2500 vs. GMT900 2500 vs. GMT900 "Fancy" (Denali/Escalade)

[CTX-SLPR]

Any more commentary on the 3rd row for GMT900s?

I think I’ll go for whichever I can get in better shape between the 6.0L and the 8.1L for GMT800. Did some reading at lunch today about improving 8.1L MPG and there’s some folks out there both with HPTuners (which I have) and EFI-Live that have testimonials on forums that they can get the 8.1L up to around 14.5 on the highway with stuff and 10.5 with a trailer. Not looked for 6.0L tunes to do the same so it might have similar gains, community for it’s bigger.

Did they sort out the DOD/AFM on the later 6.2Ls?

 

[BeXtreme]

I have a 2011 K1500 Suburban with 5.3/6L80. We bought it used a few years ago with 130k on it and its used as my wifes daily as well as towing/camping/family trip hauler. It trashed the torque converter while towing on a family trip in montana at 160k. Full rebuild and it just lost all forward gears about a week ago. It cracked the 1-2-3-4 piston while normal driving around town. I replaced that part, some seals, and put in a nice billet triple disk converter since we just recently upgraded to a larger travel trailer. It now has those upgrades, a tru-cool 40k trans cooler, and 4.10 gears front and rear. Tows great now and is at about 206,000 miles.

 

[618 Syndicate]

Did they sort out the DOD/AFM on the later 6.2Ls?

In a word, no. It needs to be deleted not just turned off.
Also, EFI live sucks for the 8.1, stick with HP Tuners.

 

[CTX-SLPR]

Looks like I'm checking out a GMT800 with the 8.1 (more because that's what it has) this weekend. I liked the GMT900 we checked out and the boys said the 3rd row was slightly more roomy than the current GMT400 but there are very few of them around that aren't white with a black gut government specials, half of which are missing center consoles and a black vinyl/leather interior in Central Texas doesn't sound as fun.

If one pops up I'll take a look at it but that's where I am.

 

[Mr Eric]

Having owned a fully loaded 1/2t GMT900 'burb...I would steer you away at this point from that generation. The 6 speed hunts (they come with 3.08 gears), mind you, mine was tuned and had the exhaust opened up...fully loaded with kids, gear, and dog, it would only do about 14.4mpg @ interstate speeds. That's real world hand calculated numbers. I will NEVER own another 1/2t Suburban (GMT400-present, solid axle rigs are different). I did own a 2500HD CCSB pickup with the 6.0L/6L90E, and it towed everything I ever wanted, but I still didn't love the interior. I think it eeked out a 15.1mpg trip one time at 68mph with a tail wind. The 6.0's need RPM to do the work, they don't have the low end grunt most are used to with SBC/BBC platforms. So be prepared to tach them out when you need to get to the useable power.

I voted GMT800 with the 8.1. A local mechanic had one that was tuned, and other than the stated oil consumption, it got similar mileage to my K2500 454 rig...with more power.

After the GMT400 rigs, the second and 3rd row room was squeezed down a bit...I would ride in the 2nd row of mine, but not the 3rd. For a vehicle that is not used everyday, and needs to be a Swiss Army Knife Jack of all Trades....go with the big block K2500 rig. Be picky, and find the cleanest, lowest mileage one you can for the money.

I second the gmt400 comment re: 1/2 ton towing. My k1500 97 burb has 4.10 gears behind/ in front of a 4l60e. The secret for me? Religious fluid changes, and towing slow.
Without the 4.10s it wouldn't be something I would do. I tow 5000+miles per year, and with trailer brakes I don't consider it completely fool hardy, though YMMV.

 

[CTX-SLPR]

Well after all of this… I’m keeping my GMT400 K2500. Someone with an undivided attention, i.e. a shop, got it sorted out and it’s running better than ever. Most critically the wife is no longer afraid of driving it. She still hate parking it but that’s understandable when pretty much all she’s ever driven is a sedan or small station wagon.
Time to invest in rebuilding the ever further decaying drivers seat and some new headlights and I think this will take us to TX and around College Station once we get there. Might even try my hand at respraying the roof to get some practice laying paint before I do my Riviera.

Feedback from test drives is that an 8.1L GMT800 is a beast of a vehicle and feels like a GMT400, just tightened and polished up. The 148k mile one I drove today was great and I really did like the cloth seats. The GMT900 I never got to test drive but crawling around it felt like it was different, not better or worse than the GMT800. The seats tumbling for example; easier to handle but I think slightly less room for cargo. Overall I think the GMT800 is a more traditional utility vehicle and better for a jack of all trades. People hauling with truck capacities on the side, the GMT900 is better though not by much.

 

[yevgenievich]

Glad the k2500 got sorted out. I had similar experience with gmt400 vs gmt800 vs gmt900. Gmt400 in the end was better to me just because of the looks being closer to my old 91

 

[618 Syndicate]

I got a GMT 800 6.0/4L65 AWD and it does exactly what I need it to do. It's a winter beater, dead reliable and the heated seats work great! I'd have recommended one but you were anti the 4L60.

 

[Dravec]

Late to the party, but I spent an awful college trip crammed in the 3rd of a '10 Burb. The trip was absolutely awesome, but I was insanely uncomfortable. I'm 6'1" and had to sit sideways in the 3rd row. My '99 K2500, I can sit straight on, and still have a couple inches or so to spare. No experience with the 800 Burbs.

 

[Papablunt]

Any more commentary on the 3rd row for GMT900s?

I think I’ll go for whichever I can get in better shape between the 6.0L and the 8.1L for GMT800. Did some reading at lunch today about improving 8.1L MPG and there’s some folks out there both with HPTuners (which I have) and EFI-Live that have testimonials on forums that they can get the 8.1L up to around 14.5 on the highway with stuff and 10.5 with a trailer. Not looked for 6.0L tunes to do the same so it might have similar gains, community for it’s bigger.

Did they sort out the DOD/AFM on the later 6.2Ls?

Between my friends and I, we've had 9 (yes, nine) GMT800 2500 8.1 Burbs.

I can say that you won't see 14mpg except on that unicorn trip where you've got gale force winds pushing you down the highway. Hand calculated, of course. The DIC lies.

The 8.1 is a great engine, but you will be getting 10-11 with or without a trailer. Tuning never did much for our fuel efficiency.

That's been our experience.