GMT900 Overland build anyone?

[BMac Attack]

The GMT 900 is a very solid platform, in my opinion. I own a 2007 Suburban 2500, it came stock with the 6.0 liter motor, 4.10 gears, G80 locking rear differential, 4l80 4 speed transmission and the two speed transfer case. It has been very reliable with the exception of the minor known issues (cracked dash, defrost tabs detaching from back glass, 4WD front axle actuator) and I've just had to do regular maintenance. It's got 134K on the ticker and shows no signs of slowing down. I've owned it for 4 years and am pretty diligent about maintenance. I bought it with 95K and changed every fluid when I bought it and haven't had any real issues except for a fuel pump that died conveniently in the garage. By the way, it has a 39 gallon fuel capacity and actually has two fuel tanks and two fuel pumps. A main 31 gallons and then an auxillary 8 gallon tank. I can easily get 400 miles of range on one tank. I could afford a newer truck, but honestly don't really need to. They are cheap to acquire and maintain. The GMT 900 comes with a 2nd battery location that is used in the diesel trucks and so I added a second battery with an isolator switch and so running the fridge or kids watching a movie is never an issue. I wired up the headlights so that the low beams, fogs and high beams can all be on at once. I changed all the interior lights to leds which was a really nice upgrade and easy and cheap to do. I'm a big guy and so I just simply don't fit in anything other than a full size domestic and this fits the bill extremely well. My biggest complaint is that the 6.0 motor is a dog in terms of power and gas mileage, but it starts and runs every time. I have installed a 3 inch lift which allows me to run 285 tires and I love the set up. It will run the freeway at 85 mph (I live out west where our speed limit is 80 mph) smoothly and still access pretty much any back road that I desire. It tows my 23 foot boat and also tows my utility trailer for runs to the landfill. Towing in the 2500 is far superior to the 1500 suburbans due to the leaf springs and larger brakes. I chuckle at all the conversations about power and towing capability that such and such a vehicle has due to it's drivetrain. The drivetrain is really secondary to the chassis when it comes to comfortable towing. It's got tons of interior room so a fridge, gear, and people all fit without even trying to tetrus stuff inside it. As I said, it's big, so I'm not fitting through narrow sections of a trail like a jeep but I just go around if I need to keep going. With the front IFS, ground clearance is not an issue since I ditched the stock front bumper. The G80 rear locker is a bit hurky jerky but it always works to get me past whatever obstacle is there as long as I air down the tires appropriately. It has every creature comfort you could ask for with heated front and 2nd row seats, leather, Bose stereo, auto lift gate, auto tumble 2nd row, remote start, front and rear climate control, etc. and fits my family of 5 comfortably. You could make a run to Costco and IKEA without having to go home first to unload in between stops. I have installed a Fab Fours front bumper with integrated winch, I also have a rear receiver mounted winch that stows inside for when I make really bad decisions. I made a home built interior storage box, and various external lights. On my wish list is to add is apple car play, an aftermarket rear bumper, roof rack, swap the captains chairs for a bench and an LS9 .

The pic included was a day with about 10 inches of new snow and I had just pulled out a 2nd gen 4 runner that was having front drive line issues. The weight of the 'Burb is a benefit when winching other vehicles, I rarely get pulled off my winching spot.

 

[charlatan]

So grateful for all the info provided here! I'm shrinking my list of replacements for my Montero (I miss V8's), and the Tahoe platform looks promising.

From what I'm reading here, my target should be an 07 or later, as long as it has the 6.2L engine, thus avoiding AFM? It looks from wikipedia that I'd need to snag a 2009+ for the 6.2L?



This wiki says the 6.2L was standard on the 4wd Tahoe... or is flex fuel standard???

6spd seems most desirable, which also puts me at 2009 or newer. I'll also check for the G80. Loose the air suspension.
Thoughts / tweaks?

 

[XJLI]

I had no idea they made 6.2 Tahoes in this generation. I wonder if those got the same 12 bolt rear as the Caddys did. If so, thats a great setup. 100% get as new as you can, the 6 spd is a must have. I've ridden in the air suspension and autoride trucks... they are so so nice. But that limits your lift options. Thankfully that stuff is really easy to delete.

 

[Martinjmpr]

Never heard of a 6.0 Tahoe. AFAIK Tahoe's got the 5.3. I don't even think you could get a 4.8 in the Tahoe and why would you want one anyway? The 5.3 is barely adequate in terms of power, so I can't imagine why you'd want a smaller engine.

Yukon Denali and Cadillac Escalade both got the 6.0 but they also have a non-lockable single-speed T-case with full time 4wd. So that's your choice: Bigger, more powerful engine and beefier transmission but no 2 speed T-case.

2009+ would be better for the 6 speed tranny and fewer AFM issues.

 

[Todd780]

2009+ would be better for the 6 speed tranny and fewer AFM issues.

Yep. I had a 2009 Suburban with the 5.3. Traded it in at 100,000 miles and never had issues with the engine.

 

[02TahoeMD]

AFAIK Tahoe's got the 5.3. I don't even think you could get a 4.8 in the Tahoe and why would you want one anyway? The 5.3 is barely adequate in terms of power, so I can't imagine why you'd want a smaller engine.

For the 2000 to 2006 at least, the 4.8 was an available option for the Tahoe. I test drove one around 2004. The 5.3 was a noticeable improvement in performance over the 4.8 and thus I refined my shopping to the 5.3. IMHO, the 5.3 for the Tahoe is plenty adequate, especially with my Black Bear Performance tune on it.

 

[charlatan]

I had no idea they made 6.2 Tahoes in this generation. I wonder if those got the same 12 bolt rear as the Caddys did. If so, thats a great setup. 100% get as new as you can, the 6 spd is a must have. I've ridden in the air suspension and autoride trucks... they are so so nice. But that limits your lift options. Thankfully that stuff is really easy to delete.

Thanks. Ya, I started searching like mad for a 6.2 and could not find one until I started searching for the GMC Yukon, at which point every Yukon showed as a 6.2.

Never heard of a 6.0 Tahoe. AFAIK Tahoe's got the 5.3. I don't even think you could get a 4.8 in the Tahoe and why would you want one anyway? The 5.3 is barely adequate in terms of power, so I can't imagine why you'd want a smaller engine.

Yukon Denali and Cadillac Escalade both got the 6.0 but they also have a non-lockable single-speed T-case with full time 4wd. So that's your choice: Bigger, more powerful engine and beefier transmission but no 2 speed T-case.

2009+ would be better for the 6 speed tranny and fewer AFM issues.

Very good info, Thx. I guess the 6spd 5.3 is the only option unless I happen upon a unicorn 6.x. All the info in that screenshot is from the wikipedia page for the Tahoe. Maybe it needs some updates?!

 

[XJLI]

I had to google it, but it’s def a thing.

2008 Chevrolet Tahoe to get 6.2-liter V-8 engine option - Auto News - Motor Trend

Chevrolet's Tahoe is joining its GMC and Cadillac GMT900 platform mates in offering GM's 6.2-liter V-8 as an engine option for the 2008 model year. Read more about the 2008 Chevrolet Tahoe LTZ engine upgrade from the automotive experts at Motor Trend.

www.motortrend.com

Like other said, I’d just make sure the big motor trucks got the 2 speed transfer case. It’s quite possible they were just AWD.

 

[charlatan]

I had to google it, but it’s def a thing.

2008 Chevrolet Tahoe to get 6.2-liter V-8 engine option - Auto News - Motor Trend

Chevrolet's Tahoe is joining its GMC and Cadillac GMT900 platform mates in offering GM's 6.2-liter V-8 as an engine option for the 2008 model year. Read more about the 2008 Chevrolet Tahoe LTZ engine upgrade from the automotive experts at Motor Trend.

www.motortrend.com

Like other said, I’d just make sure the big motor trucks got the 2 speed transfer case. It’s quite possible they were just AWD.

...and here we find the key.
"The engine, which will be offered for the 2008 Chevrolet Tahoe LTZ trim package, is only available for two-wheel-drive models and is rated at 380 horsepower and 417 lb-ft of torque. "

No wonder I couldn't find any... 2wd versions are immediately filtered on my search.

 

[XJLI]

...and here we find the key.
"The engine, which will be offered for the 2008 Chevrolet Tahoe LTZ trim package, is only available for two-wheel-drive models and is rated at 380 horsepower and 417 lb-ft of torque. "

No wonder I couldn't find any... 2wd versions are immediately filtered on my search.

well, that’s that then.

 

[CrazyDrei]

Best advise I can give anyone and everyone is stop with the online polls and question which rig to get. Go out and get the one that catches your eye, the one you will smile every time you see, the one that will draw you into the drivers seat and out on the road. That's the perfect vehicle for you. And then take it out on the dirt, learn how it drives, behaves and grow with it. Push your limits and the vehicle's limits, add or subtract accessories based on what the last trip was lacking or what you didn't even touch. Run what you have and make the best of it.

With that said, there is lots of good information here but no one's post covers everything. Mine will not either!

My 2007 Yukon XL 1500, with 37" tires, Bilstein 5100s up front and Moog HD coils in the rear with 5100 shocks.

Main reason there are not that many of us building or running them off road is because of complete lack of aftermarket support. You can get 4-6" differential drop lift that's reasonably priced, but anything more than that will cost you more than what you paid for the truck in the first place.
Secondly: who in their right mind even considers taking their family of 5, 6, 7 or 8 overlanding in the same vehicle? At his point might as well just get 2 smaller cars and have a backup vehicle when one of the them breaks down.
Finally: realistically just like any other 4x4 out there, they are extremely capable just the way they are with no modifications and that is not appealing to the uniqueness of "building" an overland vehicle rather than actually driving it it and taking it places. Guys that do that are called rednecks and hunters and camo is so not cool in the overland community.

GMT900 2007-2014 Suburbans, Tahoe, Yukon, XL are great trucks and a very capable platform just like the GMT800 2000-2006 platform they replaced. Everyone seems to keep on dreaming about the 2500 truck as the ultimate vehicle, unfortunately it's not. 1500 platform is superior. I own both a white 2500 and the gold 1500. 2500 is for towing and pavement, 1500 is daily driver and for off road driving.

The ride in the 2500 off pavement is horrific thanks to the amazing torsion bars up front and leafs in the back. Once you load it up with at least 2,000lbs of cargo or a big juicy trailer it drives very well on pavement. It barely survives off road. To make it remotely bearable on the trial (as in not get left in the dust by a Jeep) you need bigger tires, which require a lift and then you will have to throw in a lot of useless weight to make the ride smoother. Not a big deal, just be prepared to replace your ball joints every 10-20k miles.

Now 1500 chassis has it's draw backs also, 5.3 Active Fuel Management is prone to failure and its more cost effective to replace the motor than to do a DoD or AFM delete, neither one is overly complicated to do just requires replacement of lots of worn or failed parts and many hours of labor. 4L60 transmission also discourages many, however if you do not drive like a complete maniac its a very capable transmission. 6L90 in the 2500 or newer 1500 trucks is beefier and better.

This is my 2000 (GMT800) Suburban. It is the most perfect vehicle I have ever owned for serious off road travel, however due to use and abuse over last 7 years I picked up a 2007 Yukon XL for less than what I need to put into this truck maintenance and new transmission wise. Best part is that most of the drivetrain parts swap over easily from NBS (New Body Style GMT800) to NNBS (New New Body Style GMT 900) trucks. GMT900 also went to a strut(coilover) front suspension which in turn was the single best modification I did with the torsion bar GMT800 Suburban! Second one was a real Detroit locking rear differential culminated by the 37" tires.

Back to the original topic. I got the 2500 so I can pull a 24ft trailer and with hopes of making it a capable overland rig. I hit a roadblock when what I wanted to do to it cost around $14,000 in parts alone! 6" lift with coilover conversion up front, 4.56 gears, 40" tires. I went back to my 2000 Suburban which was perfect for my family and my needs. Now that the tranny went out and it needs a lot of little repairs here and there it was much more cost effective for me to buy a 2007 Yukon XL and just swap over everything I need to run my 37" tires and keep rolling for weekly adventures safer and in more comfort.

This is one outlook on the GMT900 platform that fits my needs, others may not have the time, tools, desire or resources to do what I am doing and this route will not work.

Hope at least some of my ramblings helped cloudy the water.

 

[mrpeterclark]

I really like this platform. It has it drawback - namely finding aftermarket parts. I've been slowly building out a 2007 Yukon XL Denali which has it's own pros and cons

Pros:

• 6.2L
• 6 speed trans all years (6L80 just replaced mine at 230K)
• has the larger rear diff and G80 (I'm not certain all of them came w/ a G80)
• Tons of cargo space
• comfortable for our large family of tall people. I especially like the captain chairs.
• Affordable

Cons:

• AWD single speed transfer case.
  The traction control system is actually pretty cool on these in the snow or a slick highway, but I wish they would have made these with the 2 speed transfer case. I've only really been bad off once, and it gets me where I want to go 99% of the time, but there are many times I really miss selectable 4wd and 4low. Also these trucks are notorious for throwing stabilitrak and traction control errors that seem to be caused by almost anything from spark plugs to you name it. Still chasing that gremlin. What that means is your traction control just suddenly shuts off while you're coming going up a snow canyon road and you can't put it 4wd and you're sliding all over the place.
• Aftermarket support.
  I've been super stubborn and spent WAY to much time hunting for things and making my own way.
  I was able to make a Chassis Unlimited Sierra bumper work with some modifications and I also built my own roof rack similar to Prinsu or Victory 4x4 etc. We're actually about to start producing them in the next month or so because I really see the value in these trucks and think others will.

Let me know if you have questions. I've found a lot of things that work well and where most of the dead ends are.

 

[dur66@msn.com]

It's great to find a thread that is about bigger vehicles used for overlanding. I have a 2002 Chevrolet Avalanche 2500 with 233,000 miles.

It's been a great vehicle. I'm making improvements to make it more self-sufficient and taking care of items to make it more reliable. I took my Jeep down to Baja last year for 3 weeks. My goal is to take the Avalanche for 4-5 weeks.

The Avalanche has the 8.1L engine, 4L85E transmission and G80 rear end with 3.73 gears.

I've just purchased a beefier sway bar to make it handle better on Mexico's roads and converting it to 17" wheels. The Avalanche currently uses 16". Another improvement will be modernizing the current Painless Wiring dual batter system to one made by Red Arc. The advantage of the Red Arc are fewer parts than the Painless system and the ability to use solar panels.

 

[Rosco862003]

Hello all, I currently own a 2000 LX470 which has provided 218k trouble free miles and has taken me all over US and parts of Canada. Alas, I find myself needing a bit more utility and have had my eyes on an Avalanche/Escalade EXT. I love having low range, but from what I’ve heard and read, not withstanding the above from @mrpeterclark, the 6.2 and AWD seems to work for most situations, even more so with the G80 rear.

My girlfriend and I have a little part time business setting up bounce houses which requires towing about 3k-4k every weekend for about 7 months out of the year, a task our Tundra is up to, but definitely not the LX with 33’s. Great vehicle but is a turd. Additionally, we are both considering getting motorcycles to ride together, and loading in the bed seems more convenient than getting a trailer. This would also be a vehicle that I would like to travel with just as much as the LX and still have a good degree of power, comfort, and most importantly reliability. Given this criteria, I would love one of the 07-09 Avalanaches with the 6.0 and 14bolt SF, but wouldn’t know where to begin to filter a search for one.

This leads me to my questions. I am no stranger to GM as I had a 94 Suburban 2500 that was a champ.

• Given that I will likely be towing several times a month, I’ve ruled out 07-09 and have elected to look for 09+ for the 6L80E. Will this transmission and the 5.3 be enough to handle this load in the hills of Western NC on a regular basis, and is there a gear ratio That I should look out for vs another - does it matter with a load like this?
• I don’t run hard trails, and think the motorcycle might get more seat time for harder trails, is there an ability to add a 2 speed transfer case to the 6.2, or would it be easier to just drop in a bigger motor into an Avalanche?
• Another angle I’ve considered is to keep the LX and get a cheaper GMT800, does this seem viable, or would I regret it when it comes time to attach a hitch?
• I don’t plan on lifting much more than perhaps a leveling kit and more aggressive tires, what kind of mileage do you see with the 5.3 vs the 6.2? (I haven’t ruled out the 8.1 2500 either, but know that the mileage is measured in tears now).

 

[Martinjmpr]

Hello all, I currently own a 2000 LX470 which has provided 218k trouble free miles and has taken me all over US and parts of Canada. Alas, I find myself needing a bit more utility and have had my eyes on an Avalanche/Escalade EXT. I love having low range, but from what I’ve heard and read, not withstanding the above from @mrpeterclark, the 6.2 and AWD seems to work for most situations, even more so with the G80 rear.

My girlfriend and I have a little part time business setting up bounce houses which requires towing about 3k-4k every weekend for about 7 months out of the year, a task our Tundra is up to, but definitely not the LX with 33’s. Great vehicle but is a turd. Additionally, we are both considering getting motorcycles to ride together, and loading in the bed seems more convenient than getting a trailer. This would also be a vehicle that I would like to travel with just as much as the LX and still have a good degree of power, comfort, and most importantly reliability. Given this criteria, I would love one of the 07-09 Avalanaches with the 6.0 and 14bolt SF, but wouldn’t know where to begin to filter a search for one.

This leads me to my questions. I am no stranger to GM as I had a 94 Suburban 2500 that was a champ.

• Given that I will likely be towing several times a month, I’ve ruled out 07-09 and have elected to look for 09+ for the 6L80E. Will this transmission and the 5.3 be enough to handle this load in the hills of Western NC on a regular basis, and is there a gear ratio That I should look out for vs another - does it matter with a load like this?
• I don’t run hard trails, and think the motorcycle might get more seat time for harder trails, is there an ability to add a 2 speed transfer case to the 6.2, or would it be easier to just drop in a bigger motor into an Avalanche?
• Another angle I’ve considered is to keep the LX and get a cheaper GMT800, does this seem viable, or would I regret it when it comes time to attach a hitch?
• I don’t plan on lifting much more than perhaps a leveling kit and more aggressive tires, what kind of mileage do you see with the 5.3 vs the 6.2? (I haven’t ruled out the 8.1 2500 either, but know that the mileage is measured in tears now).

Just keep in mind that if you want a 2500 you can't get it in an Avalanche in the GMT900 platform, as the 2500 Avalanche was only offered in the GMT800 platform (2002 - 2006.) So if you really want a 2500 you'd have to have either a pickup or a Suburban / Yukon XL (and in my experience, GMT900 2500 Suburban/Yukon XL's are as rare as hen's teeth. They were almost exclusively sold as fleet or government vehicles so an auction might be a good place to look for one.)

As someone who owned a GMT800 Suburban 1500 for 4 years and did a lot of towing with it, I'd have to say I can't recommend it for mountainous terrain. The newest GMT800 platform truck is now 15+ years old and that likely means a lot of small parts starting to fail. IMO the biggest weakness of the GMT800 platform is the 4L60 transmission in the 1500 models. The 2500's got the beefier 4L80 but it is still a 4 speed transmission which means that when towing up a steep grade, you're either in a gear that's too low and the engine is screaming, or it's too high and the engine is lugging.

I don't know anything about the 6L80 but it has to be better than the abysmal 4L60. I killed TWO of those in my Suburban in 4 years of towing through the Rocky Mountains.

It's really a shame because as much as I like the power train of my current F-150 (3.5 EB and 10 speed transmission), the body configuration of the Suburban was just about perfect. An Avalanche would also offer similar benefits to the Suburban, but without the 3rd row seat. The ability to drop the mid-gate and use the full 8' length of bed while still maintaining a reasonably short wheelbase is sheer genius, IMO.

With GMT900's moving "down market" we might start seeing more Overland builds. One nice thing about the Suburban or Avalanche that isn't often talked about is the larger than average fuel tank (32 gallons I believe.) Given that most 1/2 ton trucks seem to come from the factory with ~26 gallon tanks, having that extra 5 - 6 gallons is nice for range.