Square Body Suburban Info

[BCobe]

Hi all,

I have not posted here in a while but looking at getting a square body suburban for my next offroad rig so looking for some info. I currently have a 2014 2 Door JK and with an expanding family, I need something bigger. As of now, the 1973–1991 year range of Suburbans are what I am looking at. Looking for a 350 due to having 3 other vehicles with 350's in the stable. The next runner up would be a FSJ Jeep, but it seems that those rose in price seemingly overnight.

Will be doing moderate wheeling on East Coast style trails (for now anyways).
The pros to the Burb's are the solid axles, V8 engine and Size.

Negs for me are Size (in terms of breakover angle) and potential fuel economy (Currently getting 17-18mpg mixed in my JK)

Mainly looking for things to be aware of when looking at these vehicles. Things to look out for, to steer clear of, and some overall negatives about them.

I have attached a picture kind of showing the direction I might want to go.

Thanks in advance!

 

[nitro_rat]

A TBI burb will return 17 mpg highway in good tune with no lift, and 3.42 or 3.73 gears with 31-33" tires. Lifted on 37's and you'll be in the single digits.

If you're hauling family, the single a/c won't cool the back. The dual a/c is problematic when converted to 134. It will work on the highway but neither the front nor the back will blow cold in traffic. Keeping the rear heated in winter is also a challenge.

The GMT 400's really stepped up the climate control performance.

Also be prepared for things like the windshield wipers suck (especially the washers) compared to a "modern" vehicle. The headlights also aren't great. There are some upgrades available in some cases.

You will also be facing problems with wiring as all of the current for all of the accessories run through the switches. This leads to brittle and melted connections.

 

[4x4sporty]

I think Nitro is optimistic about fuel mileage. I have an 88 model with overdrive and 4.10 gears on 33 tires and my fuel mileage has been in the single digits for 20 years.
Also look at frame where steering box mounts. I have seen several that were cracked in that area.
Rust in all usual places fenders, rockers, door bottoms, quarters, tailgate/barn doors, fuel tank and frame

 

[Smileyshaun]

1990-1991 3/4 ton burb is your best bet . Tbi 350 , 4l80e trans , 14 bolt rear, 44 front and if it has a tow package it will already have 4.10s . Small lift and 35s and you will have a great stable platform .

 

[Smileyshaun]

These guys make some great products for full size chevys and here is a good example of a simple but well setup burb .

Offroad Design - Fullsize 4x4 Performance

 

[BCobe]

1990-1991 3/4 ton burb is your best bet . Tbi 350 , 4l80e trans , 14 bolt rear, 44 front and if it has a tow package it will already have 4.10s . Small lift and 35s and you will have a great stable platform .

Going to ask the question: What are you looking at MPG wise? 17mpg I can deal with, My old WJ on 35's got 9mpg on the highway and that got rough. I have the tools and ability to regear if needed.

 

[BCobe]

A TBI burb will return 17 mpg highway in good tune with no lift, and 3.42 or 3.73 gears with 31-33" tires. Lifted on 37's and you'll be in the single digits.

If you're hauling family, the single a/c won't cool the back. The dual a/c is problematic when converted to 134. It will work on the highway but neither the front nor the back will blow cold in traffic. Keeping the rear heated in winter is also a challenge.

The GMT 400's really stepped up the climate control performance.

Also be prepared for things like the windshield wipers suck (especially the washers) compared to a "modern" vehicle. The headlights also aren't great. There are some upgrades available in some cases.

You will also be facing problems with wiring as all of the current for all of the accessories run through the switches. This leads to brittle and melted connections.

Working on classic cars has yielded its fair share of wiring nightmares. Wipers I can live with because my JK's aren't that great either. Headlights, I would look at an LED route. I currently have trucklites on my JK and absolutely love them. The A/C thing might be a problem, but neither of my current vehicles really cool down the back seat to well.

 

[Buckshot62]

1990-1991 3/4 ton burb is your best bet . Tbi 350 , 4l80e trans , 14 bolt rear, 44 front and if it has a tow package it will already have 4.10s . Small lift and 35s and you will have a great stable platform .

91 is the only year square body Suburban that got the 4L80E and it was only in the 3/4 ton, 44 front came in 70's models, by the 80's all were corporate 10 bolt front ends. You never know what you will find under them today, axle or gear wise. gears depends on what was ordered. My 90 has 3.73's in a semi float 14 bolt and 10 bolt front with the tow package. In the last few years of the square body Suburban the only rule was no big block in the 4x4 package from the factory. 350 or 6.2 diesel was the only engine choice in the 4x4. Ours gets 10 mpg sometimes, 1990 2500, tbi 350,turbo 400 , 4x4, 3.73's and 285/75/16's.

 

[4x4sporty]

10 mpg is the best mine has ever gotten 6 was the worst pulling a 10000 pd backhoe. I replaced the 400 turbo factory transmission with a 700r4 which has overdrive and it didn't help much. Most of my driving is in town.

 

[SexyExy]

I had two awesome square body Subs....one 3/4 ton 1985 carb'd unit that had a very modified drivetrain and a 1/2 ton 1991 that was bone stock. Definitely spend the time to find one with barn doors. If you lift the vehicle a tail gated unit is a ********** to reach in and unlatch the tailgate unless you are really tall. Forget about asking little kids or a petite wife trying to do it. I had one of each, barn doors or nothing for me.

Biggest issue on the square bodies was the lack of quality control of GM cars from that era. Be prepared to spend a lot of time on finicky, slow and weak electric windows, door lock issues, upholstery/headliner issues, HVAC controls, weak AC, not the best windshield wiper system, etc. Nothing that stops the car from running, but the kids and wife will always be complaining.

With enough time and money, anything can be made near perfect. That is the question only you can answer.

Personally I would look at a low mileage gasoline engine Excursion or a Suburban that's 8 plus years old so it's depreciated a bunch. All of those can fit a 33"-35" tire with moderate lift/trimming and a locking traction type device in the rear diff and you'd be good to go for the kind of wheeling you're describing. Your mileage will suck regardless of what you buy....it is physically impossible to get great mileage (especially stop and go driving) with something that is high profile and 7000 plus lbs. The price difference between a low mile diesel and gasoline Excursion will buy enough gasoline to fuel your adventures for the next 10 years.

Good luck!!

 

[Smileyshaun]

91 is the only year square body Suburban that got the 4L80E and it was only in the 3/4 ton, 44 front came in 70's models, by the 80's all were corporate 10 bolt front ends. You never know what you will find under them today, axle or gear wise. gears depends on what was ordered. My 90 has 3.73's in a semi float 14 bolt and 10 bolt front with the tow package. In the last few years of the square body Suburban the only rule was no big block in the 4x4 package from the factory. 350 or 6.2 diesel was the only engine choice in the 4x4. Ours gets 10 mpg sometimes, 1990 2500, tbi 350,turbo 400 , 4x4, 3.73's and 285/75/16's.

Hmm weird my 90 had a FF 14 and a 4l80e and I bought it from the original owner . Ya your right on the front they are a 10 bolt but there’s not a whole lot of difference strength wise except for the older 8lug Dana 44s had the big hubs with larger axle shaft joints . But the great thing about a square body Chevy is you can find parts anywhere and swapping in upgrading can be done by anybody who can turn a wrench and use a floor jack.

 

[BCobe]

I had two awesome square body Subs....one 3/4 ton 1985 carb'd unit that had a very modified drivetrain and a 1/2 ton 1991 that was bone stock. Definitely spend the time to find one with barn doors. If you lift the vehicle a tail gated unit is a ********** to reach in and unlatch the tailgate unless you are really tall. Forget about asking little kids or a petite wife trying to do it. I had one of each, barn doors or nothing for me.

Biggest issue on the square bodies was the lack of quality control of GM cars from that era. Be prepared to spend a lot of time on finicky, slow and weak electric windows, door lock issues, upholstery/headliner issues, HVAC controls, weak AC, not the best windshield wiper system, etc. Nothing that stops the car from running, but the kids and wife will always be complaining.

With enough time and money, anything can be made near perfect. That is the question only you can answer.

Personally I would look at a low mileage gasoline engine Excursion or a Suburban that's 8 plus years old so it's depreciated a bunch. All of those can fit a 33"-35" tire with moderate lift/trimming and a locking traction type device in the rear diff and you'd be good to go for the kind of wheeling you're describing. Your mileage will suck regardless of what you buy....it is physically impossible to get great mileage (especially stop and go driving) with something that is high profile and 7000 plus lbs. The price difference between a low mile diesel and gasoline Excursion will buy enough gasoline to fuel your adventures for the next 10 years.

Good luck!!

Yes, barn doors are a must. One of my criterias for my next 4x4 is that it must have a solid axle. Kind of why I have discounted newer burbans. Also, want something a little older. Majority of work required I can do myself except for heavy fab work.

Thanks for everyones replys so far. Looking around, seens 10 - 18mpg seems to be the going milage for overland vehicles.

 

[CampStewart]

My .02 is that instead of regearing seek out a matched pair of axles from a 1 ton truck. Factory 4.10 or 4.56 and bulletproof.

 

[zoomad75]

There are ways to get the goals but one has to be realistic about the mileage. The TBI 350's were perfectly adequate but get underpowered quickly when running 1-ton axles and the amount of weight one can carry in a Burb. Unless recently replaced the 350 in most are going to have many miles on them. The TBI system while ok for the day, doesn't hold a candle to modern sequential multipoint injection systems. So plan on swapping to a modern engine or at least a modern aftermarket fuel injection system.

Do some digging and you'll find my buddy's 89 3/4 ton Burb nicknamed Polar Bear. He's swapped in a modern 8.1L big block, nv4500 5-speed trans, 14 bolt full floater rear axle, and early style 3/4 ton D44 front axle. Geared with 4.56 cogs in the diffs and the 5 speed it averages 12/13mpg. Every part of that swap was a bolt-in affair. A 12v Cummins would net even more potential power and better mileage, but requires a level of fab that could be beyond the average DYI home garage builder.

The mileage comes loaded or not, has no lack for power and has the ability to tow a small house too.

LS engines are another option, but stick to 6.0L or later 6.2's to maximize low end torque. They won't net much better fuel economy though.

 

[Martinjmpr]

I'd be very skeptical about anyone who says they're getting 18mpg from a gasoline engine square body.

10 I could believe. 12 on a good day.

14? Maybe, on the highway at 55mph, with no load, on street tires, going downhill with a tailwind.

People lie more about MPG than they do about HP or torque ratings. I think they're mostly lying to themselves so they don't have to admit how much money they're spending on fuel.

I'm on a couple of Facebook trailer groups where people will swear their gasoline powered tow vehicle is giving them 15mpg while pulling a high-profile, 3000+lb trailer through the mountains. I just flat out don't believe it. Yes, the little "lie-o-meter" on the dash might SAY you're getting 15, but you're not. Very few of the people who make this claim appear to actually hand-calculate their MPG.

EDITED TO ADD: You could probably get close to 18 on the highway if you put in a 5 speed manual transmission with an overdrive. But it seems like nobody wants to shift their own gears anymore. Personally I'd love to have a 6 speed manual in my F-150 but that ship sailed a long time ago.