I need your opinion. GMT800 vs GMT900. Which to buy?

[chip]

Hello all!

I'm currently stuck and I could use some opinions. I'm about to pull the trigger on another Yukon, but I can't decide between an 800 or a 900, so I'm looking to be talked into/out of both. I sold my 800 a decade ago and I still regret it. Right now, I have two Yukon's that I'm looking at and I can get them for the exact same price.

One is a '06 6 liter AWD Denali w/165K miles. The guy obviously takes really good care of it. The only thing to mention is that the clear coat is fading or peeling a little bit on the hood and on the roof, which I'm not too concerned with, because I know that this is probably the best GM drivetrain ever.

The other is a '08 5.3L 4WD Yukon SLT w/185K miles and it was owned by one guy for 18 years in Detroit and it has a good amount of service records. The interior and the exterior are really well kept. It could almost pass for a new truck. The only drawback is that it probably needs the rear end rebuilt - and I'm worried about the AFM issues with the GMT 900. I'm also not too educated on that engine/trans combo.

Knowing that information, what would you suggest I do? I'd like to buy something this week, but I can't decide. I'll take all of the input I can get - and I thank you guys in advance! I can't wait to get back in this forum with a new truck. I've missed this place and all the people in it.

 

[homesick]

The GMT800s seem to have the best reputation, overall. My experience with an '01 Tahoe fits with that. It's been in the family since '05 and has been a great truck.

joe

 

[SpareParts]

If the 06 is 3/4 ton 4X4 i would be all over it, otherwise i would go for the 08.

 

[tom3]

The 08 in Detroit. What does it look like underneath? Don't be fooled by the interior and body, and a fully sprayed or undercoated underbody is a warning. The 06 if - no rust - would be my choice for sure.

 

[swathdiver]

The 2008 will be either RWD or 4WD, not all wheel drive. Unless of course he did the conversion himself. The 2008s drivetrain is not much different than the 2006s, both have 4-speed transmissions and 3.42 or 3.73 gearing.

If you are still sweet on the 800 platform, get the '06 Denali. The Gen IV LS engines are more enduring and make more power and those with AFM can be either turned off or deleted.

Which one do you not mind spending the most time in? Get that one!

 

[chip]

@SpareParts I'm not sure if the '06 is 3/4 ton or not. I think it's a 1/2 ton. *EDIT: It's a 1/2 ton.

@tom3 Both have very minor rocker rust, but the frames are good.

@swathdiver My fault. I meant to say the '08 was 4WD. I have to admit that I really want to prefer the 900 platform. I like the newer vibe of the '08. I've just been hearing all kinds of horror stories about the 900 platform - but I also know how that goes (complaints are always louder than compliments). I'm trying to parse out the truth from the fiction and the fact that the '06 is a Denali, with 20K fewer miles, and the 6.0L - with both trucks being the same price - is making this harder than it needs to be.

 

[swathdiver]

@SpareParts I'm not sure if the '06 is 3/4 ton or not. I think it's a 1/2 ton.

@tom3 Both have very minor rocker rust, but the frames are good.

@swathdiver My fault. I meant to say the '08 was 4WD. I have to admit that I really want to prefer the 900 platform. I like the newer vibe of the '08. I've just been hearing all kinds of horror stories about the 900 platform - but I also know how that goes (complaints are always louder than compliments). I'm trying to parse out the truth from the fiction and the fact that the '06 is a Denali, with 20K fewer miles, and the 6.0L - with both trucks being the same price - is making this harder than it needs to be.

The 900s are better overall. They are more fuel efficient, enduring, reliable (when AFM is taken out of the equation) and make more horsepower. Couple that with the 6L80 transmission in the 2009+ models, those are towing beasts.

There are aftermarket digital dash displays now and some new navigation displays that update the look and capability of the trucks.

If you buy the 2008 and AFM is still active, run the same oil that the owner was using for a time. If you change it abruptly with a high detergent oil, such can break loose years of accumulated sludge and mess with the oiling system and AFM. There are plenty of posts on how to do it right and wrong on here.

 

[West 1]

For Hauling, lumber, furniture etc the 06 is a better platform as the middle bench folds into the floor flat. You can sleep in there if camping. The 07 and newer don't offer the flat floor middle seat when folded down. For me, my suv is also my truck, I haul everything in it. I sold my perfect condition 03 Yukon and kept a 2008 Denali last year. Still kind of regret that choice but Mama preferred the Ride quality in the 08.................

The 07 and newer Dash boards all crack and rattle, there is a plastic dash cover for around $200 that covers it well and looks near perfect and fixes that. I have installed 3 now, including this current Denali.

The 07 and newer steer better with rack and pinion and seem to turn a little tighter if needed. Small advantage but helps for me, my trailers are in a very tight spot and I use every inch putting them away and taking them out.

The radio in the 07 and newer has crap buttons and the black plastic comes off leaving the dash looking low class. Radio works fine, looks terrible.

I miss having low range in the 08 Denali, Low range allowed easy moving of the trailers in those tight spots backing them in uphill and around tight corners. Also missed it trying to pull out a stump last year. Low Range for me is a good option to have in a 4x4 vehicle.

Other than AFM in the O8 5.3L the engines are almost identical. The 6.0L is a good engine but does use more gas than a 08 5.3L. Probably 1-2 mpg difference but it runs stronger.

I have repaired many 5.3L's when the AFM fails. If you can't turn a wrench that is very expensive in a shop. If you can turn a wrench and have tools for me I use around $1300 in parts, while the heads are off you can have a valve job done for $600 or so.
When I do that job it also gets a new water pump, thermostat, all new hoses and belts and idler pulleys. They are included in the $1300 parts price estimate along with all new lifters, guides and AFM manifold, oil pressure switch, oil pan removal for new pump Oring.

I can't see tearing into one and not making it reliable.

I did a couple AFM deletes before learning more about Fed emissions laws and fines on shops doing that work. At that time there were no 50 state legal AFM delete kits. Between 2019 and 2025 I did several of these but have tried to retire since.

I had a 4L60 fail in my Denali with a 6.0L at only 59,000 miles, GM told me to pound sand, no warranty.

I had an Escalade that lost the 6L80 at 175,000 miles. Same Escalade with a 6.2L dropped a valve seat and broke a piston at 173,000 miles so anything can break and used cars are a gamble.

I am not a fan of Peeling Paint. I don't do body or paint work so bad paint is a deal breaker in my book. Paint jobs today are super expensive.

Did not give you an answer but a few things to consider. If I needed a reliable family hauler I would search and find a low mile, (50,000) rig and pay extra to buy it, miles wear out parts and there are lots of wear parts on these trucks.

 

[Prospect62]

I've had an OBS Yukon, a GMT800 Tahoe, a GMT900 Tahoe (current) and a K2 Suburban.

The bottom line is, as GM trucks modernized and "improved", they simultaneously took some steps back in reliability (in the name of saving fuel and emissions).

I'm not sure what your circumstances are and why you're in a hurry to "buy this week" but if I can give you any advice it would be to consider searching for something you really like, not just what's around right now. For your own sanity, try to avoid anything that's been subjected to over a decade of rust belt winters. Why you would consider buying anything with rocker rot and faded paint when you really don't have to is beyond me. I sold my 2016 Suburban because the rockers were soft and rotted after only four central New York winters. I won't put up with it.

 

[Chris2144]

I have owned numerous obs and nbs pickups. Also a 2002 Tahoe. And now have a 07 Yukon Denali.
The 07 has 162k on it and it has had alot of little issues and a couple major ones right when I bought it.
The 2002 Tahoe only had one major problem the whole time I owned it.

GMT 900
6l80 needs to have a trans tune and the torque converter replaced this is just a common issue with them.
Also the afm needs to be deactivated.
There are other little things but not to major.
Gmt800
4l60 is the downside but if taken care of can mast a long time. I would check the casting number on the heads I believe it was 862 heads were a bad cast and were so porous that coolant would seap through into the rocker area this is what happened to mine iirc that issue was fixed by 06 and I believe the 6.0 does not have this problem.
I sold my 02 with 216k miles on it and it is still running around today with the stock 4l60.

It would be a toss up to which is in better shape.

 

[chip]

All good points. I appreciate the feedback. @Prospect62 Having lived in Florida for 30 years, I've never really had to deal with rust, so I have to admit that I'm not sure what I'll be getting myself into with the vehicles up here. If I could find something similar in Florida, I'd buy it, but then I have to worry about whether or not it's been flooded, so it's 6:1 half a dozen the other is how I'm trying to look at it.

 

[West 1]

I sold my 2003 Yukon in perfect shape with 135;000 miles last April for $8000 which was a high price in California. The buyer shipped it to New York where he said these bodies with zero rust were worth double. Wish I had looked into that in advance.

 

[Prospect62]

I sold my 2003 Yukon in perfect shape with 135;000 miles last April for $8000 which was a high price in California. The buyer shipped it to New York where he said these bodies with zero rust were worth double. Wish I had looked into that in advance.

True story.

I've shipped in a few Crown Vics and a Marauder from out west and the clean body and undercarriage adds enough value around here to pay for the shipping and then some come resale time.

Like I said, a brand new Chevy truck will only last you about 5 years here before rust starts showing on the body. If you're lucky and care about it, 10 before important undercarriage parts disintegrate.

This silver 2012 I now own came from southern New Jersey and while not perfect, it's probably the nicest GMT900 in my county and there aren't very many left anyway.

 

[strutaeng]

OP, have you crawled underneath each vehicle? I bet that would be the biggest deciding factor here.

I was once looking for an engine harness for my 99 and I was "lucky" to find this Z71 truck at the wrecking yard that seemed pretty complete on the engine bay. I started removing sensors and when I finally crawled underneath I almost threw up...suspension and everything looked like it was pulled from bottom of the Titanic wreckage. I had never seen vehicle rust up and personal. I asked the guys there and they told me that truck had come in from Chicago...

 

[chip]

This is all good feedback. Thanks to everyone who commented. I'm going to look into some southern examples.

 

[Bronson357]

Ok my 2 cents, I own a 2000 extended cab pickup, 02 suburban, a 07 rwd tahoe and 2012 burb . The gmt 800 are far superior IMO, much more comfortable and so forth, the 900 is more vanity. The 800 are much more comfortable to IMO and far cheaper to maintain I guess? All are 5.3, burbs with flex fuel capability, truck and tahoe no!! Probably doesn't matter, both 800s have 4.10 gears, tahoe 3.42, all 4l60e, 2012 3.08 and 6l80. All have close to 200 miles on them. They all have little quirks but the 800 seem more comfortable, but it is nice to have remote start and such on the 900s and stuff like that.
Imo also the 800s are cheaper, more reliable and such. Plus enough electronics to get by and not the nuances of way to many electronics in the 900. The steering and drivabity of the 9s is much more car oriented, 8s more truck like! My friend has a k and there are so many dash lights, cuts of when to warm and seems to much brother bear. Definitely is nice but I would not take 1000 miles without aaa

I would never buy one from the east coast unless clean, clear coat and interior is far easier than a rusted frame, rusting rockers just lead to a whole lot more.

I would much rather, replace,engine and interior than rust. Good luck

 

[Sir_Hiro]

I only went with a 900 because I've never had any luck with the past 5 4l60E Trucks/Suvs I've owned besides my 00 Diamond Edition Jimmy. The 800s are way more plush, not so much cheapish plastic. You also gotta think of it like this as well lots of these 800s are going to be nearing 25 years old. No matter what Series you buy you have to be prepared to do some repairs on it. Low Mileage ones are nice but that tells me they were barely driven and will likely need more TLC to get to a DD status.

IMO Either one is a good buy. Each has their own issues that are easily fixed. Neither Series has any major issues to be scared of.

 

[intheburbs]

I'd go with the 06. Lower miles, no AFM.

Personally, I won't own a truck with AFM.

If the 08 has all the bells and whistles - sunroof, remote start, power/remote tailgate, heated seats, etc - you might decide that offsets the risk of AFM. Certainly check underneath for rust.

 

[Bronson357]

If I had my choice and could find a decent one I would love to find an 06. Like mentioned earlier the 800s are getting hard to find unless you go to the junk yard lol. 900s are everywhere. 08 is a good year to most. Good luck let us know

 

[chip]

Thanks for all the feedback guys! I appreciate you.