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 sort. In my opinion, the H3 was meant for exploring the path less traveled. Making an H3 anything less than 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 Hummer represents as a brand.

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 and a floor leveling platform 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 off-road 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 a 35-inch tall tire, is the biggest tire that can be bolted onto 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 absolutely 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 two bolts connected to the torsion bars. Watch either of the two YouTube videos below to get about 2-inches of lift out of the front-end suspension in less than half-hour. Remember that the H3 Hummer will need an alignment after cranking the front torsion bars. Do Not Buy Torsion Keys from any manufacturer. These people are selling complete junk to you. They’re the modern-day equivalent of a Snake Oil salesman.

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. These videos demonstrate 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-inches higher in the front and 1.25-inches in the rear.

After “Cranking the Torsion Bars” I recommend purchasing some good quality extended length shackles for the rear suspension. Below is a YouTube video of installing the 1st generation extended shackles. The combination of cranking the Torsion Bars and bolting on some extended shackles to an H3 Hummer raises the hummer’s height approximately 2-inches in the front and 1.25-inches in the rear for less than $125.00 and a wheel alignment. I recommend avoiding any shackles with a thickness less than 1/4″ (For example ReadyLIFT).

Even though the front torsion bars can be physically cranked more, the additional lift will drastically reduce the life span of the front axle driveshafts. This is why the max the torsion bars can be cranked on H3 Hummer is 24.5-inches from the center of the front rim to the bottom of the fender. The center of the wheel can be found by the center dash of the “H” in Hummer on the factory H3 Hummer hub cap on the center of the rim.

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. 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 off-road suspension.

Skidplates, Underbody Protection

If there’s a way to put a bigger tire under the H3 Hummer, I’m just going to find a bigger rock to crawl over. Eventually, the H3 is going to run out of ground clearance and bottom out. Without skid plates, bottoming out on a rock, trees, and mud can cause serious issues to the vehicle. Good skid plates make it easier for the vehicle to slide over rocks, trees, and mud. Reducing the chance of getting stuck on things off-road. Secondly, they offer protection for those undercarriage components that allow the Hummer to get home under its own power. Without the protection, parts can get damaged. The important parts like axles, driveshafts, and the transfer case need to be protected so that all the tires can keep spinning. Finally, well-designed skid plates will enable the H3 Hummer to go to places the vehicle was never intended to go. That is why I have the H3 Hummer Heavy Duty Skid Plate Underbody Protection.

Winch Mounts

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. There are no style points for winching over an obstacle. But who cares how you made it down the trail? So the first thing to figure out is how to mount that winch. That is why I created the H3 Hummer Hidden Winch Mount. This winch mount conveniently hides an 8,000lb or larger winch behind the factory bumper. The clutch is easily accessed by reaching through the radiator grill. This design also helps protect synthetic lines by keeping them out of direct sunlight. The sun’s damaging UV rays are the biggest reason synthetic winch line breaks. The Hidden Winch Mount’s design also helps keep the synthetic winch line free of ice in the winter. And has a near-perfect OEM look to it.

Radiator Upgrade

Do not buy aftermarket aluminum radiators like the CSF Heavy Duty Hummer H3 Radiator or the Ron Davis 1-16H3T Radiator. Do not buy the cheap knock-off H3 Hummer radiators from Autozone, Oreilly’s, and etc. A GM Genuine, Part Number #25964054, radiator from RockAuto.com is the best choice. The factory GM Genuine radiator is of much better quality and will last much longer than any other option. I use to recommend aluminum radiators. I no longer do because mine leak a bunch of times. CSF customer service was bad and never got help replacing my radiator.

OEM Part Number: 25964054


When the shocks need to be replaced there are a bunch of options. Two brands of shocks perform better for the H3 Hummer than any of their competitors. The first and best option are Fox 2.0 Performance Series IFP Shocks. Fox 985-02-009 shocks upfront and 985-24-048 shocks in the rear. The second best option is Bilstein’s B8 5100 shocks. The Bilstein part number in the front is 24-186643 and the rear suspension part number is 24-185615.

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 provides an easy-to-understand report of the vehicle’s 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 me, 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 a GM 10-Bolt solid axle in the rear. The GM 10-Bolt uses an 8.6 ring gear and is typically interchangeable with the 8.5 ring gear products. 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.

Learn why so many differential covers are of bad design from Banks Power Video on YouTube.

In the rear, I recommend the ARB 4×4 0750007B Differential Cover for the rear axle. I have had my diff cover on my H3 for years. It has been functioning perfectly and I enjoy it. However, use a thicker gasket like the Lube Locker GM 8.5″ when installing. I know of a few H3 owners that had clearance issues. Worst case scenario, an angle grinder and two minutes can fix the minor clearance issues in this photo. You might ask, “Why defend a diff cover that needs more clearance?” For the full answer, check out the YouTube video with Gale Banks and aftermarket diff covers. It has to do with the protection and smooth flow of the oil within the differential cover.

For the front axle, I’m convinced the 7.5 differential cover Summit Racing® Manufacturing and Engineering Differential Support Covers SME-8510400NL will add additional rigidity to the front differential housing. I haven’t installed this product. I don’t know about clearance issues but I think this could add improvement with issues of the factory differential under high torque loads distorting.

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

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