H3 Hummer, Guide

This is my personal guide to building out the H3 Hummer for off-road. I’m not the person to ask questions about chrome, 20-inch rims, step-bars, lowering, and those things of the sorts. In my opinion, the H3 was meant for exploring the path less traveled. Making an H3 anything less than of an explorer is just a shame. Whereas improving upon the stock off-road abilities of the H3 and going further than the vehicle was ever intended is the best way to honor the idea that is the brand Hummer.

This passion for the H3 Hummer began with designing Rock Sliders so that I could protect the rocker panels when I ran out of ground clearance off-road. More products like High Clearance Leaf Spring Bolt Plate, Extended Shackles, Under Body Protection Skid Plates, and even more products have made their way into my H3 Hummer Off-Road Parts Store. Even now (Aug 19th, 2020), I’m still working on new designs of products I wish that I could buy for the H3. Currently, I’m testing a Hi-Lift/CB Antenna/Bottle Opener/Jerry Can Holder mount, 1-Ton Steering Tie-Rods, and a Tool Box/Safe for the trunk.

JOIN the Forums!

Looking for the answers to your H3 owes? Maybe you want to show off those pictures of vehicles war paint. Basically, if it has to do with the H3 Hummer, hit up these two groups. The Hummer 4×4 Off-Road is Like Nowhere Else. Called H40 for short, the forum for HUMMER, 4×4, and Off Road fans. And then there is the Facebook group H3 Off Road, which is just for us H3 owners. Share pics info tech tips anything you want, try to keep it h3 related.

What’s the Biggest Tire? 35″

315/75r16” is the answer to the most asked question about the H3 Hummer, “What is the biggest tire you can bolt on to a stock H3 Hummer”. 315/75r16, which is often referred to as 35-inch tall tire, is the biggest tire that can be bolted on to the factory H3 Hummer without the need for a lift kit or any modification. Just drive to the local tire store, pick out any tire sized 315/75r16 and drive away. There will be zero issues. “315/75r16” equates to a tire that is approximately 34.6 inches tall, 11 inches wide, and mounts on a 16-inch rim.

I need to dispel some miss information about bolting 315/75r16. The local tire guy probably knows just what the computer tells them. That computer is going to tell them that 315/75r16 don’t fit. I promise you that the 315/75r16 tires mount perfectly and will bolt onto the H3 perfectly fine. The tire salesman may try to say that the tire will not fit on the rear tailgate, but again I promise the tire will fit fine. If there are any issues, just show the photo below of my bone stock H3 Hummer with a brand new set of 315/75r16 Red Letter General Grabbers.

H3’s First Lift Kit

The H3 Hummer’s first lift kit begins with just tightening the bolt connected to the torsion bar. After “Cranking the Torsion Bars” I recommend purchasing some good quality extended length shackles for the rear suspension. Cranking the Torsion Bars and bolting on some extended shackles to an H3 Hummer raises the height approximately 1.5″ in the front and 1.25″ in the rear. The front can be raised higher. However, the front driveshafts with have excessive wear and tear from any taller ride height. Finally, look out for manufacturers that sell parts that accomplish absolutely nothing. They’re the modern-day equivalent of “Snake Oil” salesman.

Any company selling “Torsion Keys”, “Extended Jounce Shock (which may also be called bump stops)”, and “Shock Extensions” are just trying to take advantage of H3 Hummer owners. Speaking of taking advantage of people, ReadyLIFT SKU 69-3070 is the “lift kit” that gives me the most amount of anxiety. The torsion keys they include in that “lift kit” do nothing, the factory torsion keys work perfectly fine for lifting the H3 Hummer frontend. Just tighten the bolt for the desired ride height. The shock extensions don’t help either because the range that the suspension can travel vertically from absolute top to absolute bottom doesn’t change at all with their lift kit. The only thing that does change is the ride height. The factory shocks work perfectly fine through the entire range that the suspension can travel. This is what’s called the suspension’s cycle, the range the tire can travel vertically. It is disheartening that they claim only 32″ tire will fit because they’re too lazy to create a second listing for the H3 Hummer vs the GM Colorado / GMC Canyon. 35-inch tires will fit perfectly fine on a completely stock H3 Hummer suspension. Unless building a mall crawler, the worst offender out there is the Extended Jounce Shock. Extending the jounce shocks takes away from the “Up-Travel”. Up-Travel is the distance that the tire can travel up from ride height until it bottoms out against the frame. Limiting the distance that a vehicle’s suspension can travel upwards is never a good thing for improving the suspension for off-road.

So now that I’ve covered what to avoid with the H3 Hummer’s first lift kit, let’s talk about the one part and the one tool needed to lift the H3. The only off-road part that is needed is a longer set of shackles for the rear suspension. I have heavy duty extended shackles for sale on my website. I recommend avoiding any shackle with a thickness less than 1/4″ (For example ReadyLIFT). The only tool you needed to lift the front suspension on an H3 Hummer is a 26mm or a 1-inch and a 1/8 socket to tighten the torsion bars bolts. The video demonstrates perfectly how to crank the torsion bars to desired front suspension ride height. After cranking the Torsion Bars and installing extended shackles the H3 Hummer should be sitting approximately 2″ higher in the front and 1.5″ in the rear.

Skidplates, Underbody Protection

Even if there’s a way to put an even bigger tire on the H3 Hummer, I’ll just find an even bigger rock to crawl over. Which is why the h3 needs a bit more protection than what the bone stock one comes with. When the H3 Hummer first showed up at dealerships, owners could order the OEM Underbody Protection. But in my opinion, the OEM skid plate has some serious flaws. First, there are plenty of photos where the H3 got hung up on something and just the weight of the vehicle destroyed the skid plates. Second, the OEM skid plate design wastes precious inches of ground clearance. I need every inch of ground clearance I can get. Moving on, every single part of the design is a great snag point, making it easy to get the Hummer hung-up on obstacles. This demonstrates how the OEM skid plates were just an afterthought. What’s even worse, is that GM produced so few of these skid plates that scarcity has made them worth a fortune.

Since the OEM skid plates are a failure from a design perspective. I needed some real Underbody Protection, basically, overkill is what is needed. And that’s exactly what I’ve created. Let me introduce you to the H3 Hummer Heavy Duty Skid Plate Underbody Protection. The parameters consisted of making them strong. At 1/4 inch thick, the thickest of all the H3 Skid Plates currently available, they are strong enough to support the entire weight of the vehicle. Next, I needed to eliminate all the snag points, that way the H3 can’t get hung up on the rocks, trees, mud, and whatever else happens to get underneath there. I fixed the issue with the OEM Skid Plates robbing the H3 of precious ground clearance. One thing I didn’t expect to improve so much with skid plates, was how much better the H3 was able to navigate the off-road trail. This kind of improvement is something that typically is only possible with improving the suspension or increasing the traction to the tires of the vehicle. The skid plates are extremely impressive when dropping down into thick ruts on a muddy trail and feeling how much easier it is for this H3 Hummer to slide down the trail. Anyway, enough talking about these HD Skid Plates, head over to my store and get a set for yourself.

I’m not the only guy into town making skid plates. To find the OEM skid plates, you can always try to get lucky on eBay or some website searching for the part number GM# 12498474. My buddy at Thor Parts has a fix for the OEM skid plate called the UCP BEEF-UP SKID PLATES made from 3/16″ steel that welds onto the bottom of the OEM Skidplates. Knight Metal Works makes the H3 UCP Up Armor System!!! 3/16. Now, Knight Metal Works makes the claims that his skidplates drain water, mud, and dissipate heat better…. but I argue this is a moot point. However, I’m not sure if Knight Metal Works is still around…

Winch Mounts

Single handly the most important tool for off-road has to be a winch. I’d argue that a winch is even more important than lockers and tires. Sure there are no style points for winching over an obstacle, but honestly… “Who cares how you made it down the trail?” So the first thing to figure out is how to mount that winch. I designed, manufactured, and sell the H3 Hummer Hidden Winch Mount. My winch mount conveniently hides an 8,000lb+ winch behind the factory bumper. The clutch is easily accessed by reaching through the radiator grill. My design helps protect the synthetic lines by keeping them out of the sun’s damaging UV rays and free of ice in the winter. And has near-perfect OEM look to it. However, if you like to purchase something different my buddy at Thor Parts used to sell the H3/H3T GEN II FRONT WINCH BUMPER. Finally, if you have excessive amounts of cash lying around, check out the Predator H3 Winch System.

Radiator Upgrade

I’ve noticed a large amount of H3 Hummer owners having issues with their radiators. However, I have 150,000+ miles on my H3 and have never had any real issues to date so far. The problem typically is because of the radiator pulls double duty for both the coolant and also the transmission fluid. If the fluids ever mix due to a broken seal or seem it will destroy the transmission very quickly. So the options are to buy another factory plastic one…. (cue the crickets chirping) or you can upgrade to the CSF Heavy Duty Hummer H3 Radiator or the Ron Davis 1-16H3T Radiator. They’re premium all aluminum radiators that sure to outperform that plastic on the H3 comes with from the factory.


It’s been over 12 years since the first H3 Hummer came off the assembly lines. There’s no denying that our vehicles are getting older and will eventually need parts replaced. The shocks from the factory are amazing, but they don’t last forever. When they need a replacement there are a bunch of options, but a few of them stand above the rest. The first option to a look at as is the Fox 2.0 Performance Series IFP Shocks for the front 985-02-009 and rear 985-24-048. Next up is the Bilstein B8 5100 – Shock Absorber for the front 24-186643 and the B8 5100 – Shock Absorber for the rear 24-185615. These seem to be the most popular. Sure there are a bunch of other brands of shocks, but most find them in be inferior quality compared to these two brands. I personally run a set of Fox Shocks, and that is what I recommend. Just make sure to use PB Blaster on those bolts before removing them.

Getting Your Oil Checked

Next time that vehicle is up for an oil change, I recommend getting the used oil analyzed at Blackstone Laboratories. “Oil analysis is a quick, nondestructive way to gauge the health of an engine by looking at what’s in the oil.” Source Located in Fort Wayne Indiana, Blackstone Laboratories provide an easy to understand report of the vehicles engine condition. The test kit from Blackstone is completely free, so there is no reason not to have a test kit laying around. Head over to this page and fill out the form to get a test kit. The process was completely painless for myself, and even caught an issue that I had been overlooking.

Heavy Duty Differential Cover

The H3 Hummer has AAM 7.6 IFS in the front and GM 10-Bolt solid axle in the rear. Those gears could use some protection and additional strength. That’s where an aftermarket Heavy Duty Differential cover comes into play. This way the gears that are set to within 5-thousands of an inch are safe from damage. For the rear axle, I recommend the ARB 4×4 0750007B Differential Cover. Don’t worry that Amazon says the ARB Diff Cover doesn’t fit your H3 Hummer. I have had my diff cover on my H3 for months now and it has been functioning perfectly. And while I haven’t tried it yet, I’m convinced the 7.5 differential cover Summit Racing® Manufacturing and Engineering Differential Support Covers SME-8510400NL will do a great job of adding additional rigidity to the front differential housing.

That’s all for now!

I know of a lot more information about the H3 Hummer that needs to be added to this list, but that will just have to wait for another day.

List of PDF files for the H3 Hummer

Hummer H3 – Airbags
Hummer H3 – Anti-lock Brake System
Hummer H3 – Automatic Transmission
Hummer H3 – Bolted Exterior Body Panels and Closures
Hummer H3 – Bumpers & Fascias
Hummer H3 – Cellular, Entertainment, and Navigation
Hummer H3 – Clutch
Hummer H3 – Cruise Control
Hummer H3 – Disc Brakes
Hummer H3 – Displays & Gages
Hummer H3 – Electrical Components
Hummer H3 – Engine Exhaust
Hummer H3 – Engine Cooling
Hummer H3 – Engine Mechanical 3.5L
Hummer H3 – Engine Mechanical 3.7L
Hummer H3 – Engine Mechanical 5.3L
Hummer H3 – Exterior Trim
Hummer H3 – Fixed & Moveable Windows
Hummer H3 – Frame & Underbody
Hummer H3 – Front Drive Axle
Hummer H3 – Front Suspension
Hummer H3 – Getting to Know
Hummer H3 – Horns
Hummer H3 – HVAC 2
Hummer H3 – HVAC
Hummer H3 – Hydraulic Brakes
Hummer H3 – Interior Trim & Paneling
Hummer H3 – Lighting
Hummer H3 – Maintenance & Lubrication
Hummer H3 – Manual Transmission
Hummer H3 – Mirrors
Hummer H3 – Owners Manual
Hummer H3 – Parking Brake
Hummer H3 – Power Seats
Hummer H3 – Power Steering
Hummer H3 – Propeller Shaft
Hummer H3 – Rear Drive Axle
Hummer H3 – Rear Suspension
Hummer H3 – Seat Heating and Cooling
Hummer H3 – Service Reminder Indicators
Hummer H3 – Steering Wheel & Column
Hummer H3 – Sunroof
Hummer H3 – Transfer Case
Hummer H3 – Vehicle Access
Hummer H3 – Wheel Drive Shafts
Hummer H3 – Wipers & Washers
Hummer H3 – Wiring 2006
Hummer H3 – Wiring 2007
Hummer H3 – Wiring 2008

  1. Wish I could have found these links yesterday. Just got done replacing my A/C condenser and it would have gone much smoother had I had it. Oh well, it’s good to know that I got it out and back in the correct way! Thanks for posting these – you’ve been bookmarked!

  2. Just want to say thanks. My H3 is a 2008. In your opinion, can I use this 2007 info, or should I not even try? Thanks again brother.

    1. For a new owner This website is great and very helpful. I’m glad i finally found something for my h3. Thank you for your dedication!

  3. This is awesome! I am going to be placing my order for your aux in. Thank you so much! You just saved me a ton of money on a new radio! The information is also very helpful since I have to track down some wiring issues!

  4. Hello,
    I am hoping to find a solution to my H3 that keeps shutting down as soon as I start the ignition, in a second. Something to do with the anti-theft system, have tried to reset it but nothing works. All the diagnostics say all systems are functioning as normal.
    Any advice is appreciated

  5. I have a 2006 H3. All stock but thinking about making some changes. Currently have 265/75R16 tires. Do you know if a 285 will fit without any kind of lift? Looking for the best tire/wheel combo I can get to accommodate more off road travel. If I do have to lift, what is the best possible way to achieve the amount of lift required to fit a 285 tire? Thanks!

    1. I have 285/75R16 Cooper Tires on my 2007 H3, look great, no problems besides growl on the highway, sorry for delay and hope that helps.

  6. Hey,
    Love my H3, biggest concern I have is that since Hummer is defunct the parts will dry up or become hard to get. I recently had someone point out to me that while HUMMER is gone, GM is not and since they are the true manufacturer we will be good to go for decades to come. Do you agree? Is this a sinking ship?

  7. Just bought my first Hummer; (2007 H3), already cleaned the throttle body and am going to replace the CV drive shaft axles and your site is the ‘Cat’s Meow’! Kids are grown/off to college and wife and I can now spend more time on the water and trails, I prefer to do maintenance on equipment myself and your website will be my GOTO source. Thank You for your hard work in this site development and very much appreciate the details!

  8. Just replaced the rack and pinion and power steering hoses on my H3 and now it is throwing a “service stab sys” message? Any idea why?

  9. Do you have wiring diagram for factory 2008 H3 Back-up Camera kit? I have the factory rearview mirrow with the Onstar and the camera that pops out when shifted into reverse. Need the wiring diagara so my guy can connect a camera.

  10. Hey there! Great website, lots of info though I am curious to the one thing I couldn’t seem to find. Been having an issue with my front seat’s trim panel over the power controls. I think I need to replace the clip that holds it to the seat as well as the foam as its pretty mashed down (The foam that is) Do you have any info on replacement or clips for the front drivers seat trim panel with the power lumbar? I kept finding references to it in the pdf manuals but couldn’t find the info itself with picture or diagrams. Any help would be great! I love my 07 Black beauty!

  11. Can the rear of a H3 be lowered to level it with the front rather than lifting the front to level with the rear/
    I am not a fan of lifting as it has a negative affect on the ride quality on highway driving.

    1. I think they’re great tires, especially in mud and great for a pavement pounder. I wouldn’t get them if the vehicle was a trailer queen and never saw asphalt.

  12. FYI
    Found a 10 bolt welded diferential cover made by chassis unlimited. I think Livermore California. Works well and I prefer the welded rather than cast units

    1. I just went to Chassis Unlimited’s website to see their differential covers and they certainly make a bunch of good-looking designs. However, there are a lot of companies that make stronger than factory differential covers that will work with the H3. If I go through the effort to have every single differential cover I find to add more value to the page. Seeing as you took the time, I’ll add a few more differential covers for the H3 Hummer’s 10 Bolt. Specifically, my favorite welded one.

  13. Just wanted to thank you Schwarttzy for the time, effort and excellent information you’ve put out here. I’ve been a Auto Tech for 30 years, and purchased my first 07 H3 in 2007 and currently have 186000 miles on it (hard miles). Just purchased another H3 08 Alpha, and you could not have nailed what to look for and do, and what to expect and improve with these models! Good work.

  14. Thank you for all the information! You have helped me through many projects on my Hummer through the years! So, Thank You. Quick question for you I have a 2009 H3 Hummer, do you know if there is a different wiring manual for this year vs 2008?

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