HUMMER
I drive a 1992 HUMMER from AM General.
My truck is a 4-seat half-door open-cab 1992 model, colored tan with black highlights. It has the standard undersized Hummer brushguard, a 12,000 pound Warn electric winch, extensive rocker panel and underbody protection, auxiliary PIAA spot and fog lights, and a swingaway spare tire carrier that also mounts my 5' Hi-Lift jack. I've replaced the stock Hummer axles, namely Zexel-Torsen torque biasing differentials based on the AMC 20, with ARB Air Lockers. To simplify maintenance and improve cabin space, I've hacked the interior cabin extensively. For tires I run Interco Swamper TSL SXs during mud and snow seasons, and Goodyear Wrangler GSA radials during drier seasons.
My truck currently has enough scars, dents, and poorly repainted patches to pass for a military surplus model. I think it looks fine that way.
I've spent a lot of time in this truck, both sitting the driver's seat and lying under the body, since for almost nine years and 100,000 miles I had no other vehicular transportation. This is its story.
Where I Got It | How It Drives | How Much It Costs | About Maintenance | Where I Drive It | Stupid Hummer Tricks | Specifications | Bibliography
As one of the very first civilian Hummer models made available, my truck bears the legend Limited Edition #151. At the time (1992), AM General sold Hummers directly to the 300+ of us crazy enough to buy one that first year. To get mine, I flew out to the factory in South Bend, Indiana, then drove the truck back to Seattle.
The next year AM General sensibly transferred all civilian Hummer retail and support activity to franchised dealerships around the United States. In the Puget Sound area, that's Doug's Lynnwood Hummer in Mountlake Terrace, WA.
If you're looking for a used military model, try checking the advertisements in Military Vehicles magazine, or try the publications of the Military Vehicle Preservation Association, Army Motors and Supply Line, reachable at 800-365-5798. (You might find a driveable or almost-driveable military surplus model here, or here.) Be warned, however, that the US DOT in its infinite wisdom has decreed HMMWVs inherently illegal to drive on public highways, due to nonstandard lighting, lack of proper emissions control equipment, and a failure to pass the side collision test. Furthermore, the US military scraps almost all of their surplus trucks, vending the crumpled and cut remains through the Defense Reutilization and Marketing Service. (If reassembling a HMMWV from scrap appeals to you, try the DRMS National Sales Office at 800-222-DRMS.) Here we have a fine example of our tax dollars hard at work: I know I certainly feel safer - don't you?
You can find good values in used civilian Hummers by calling around the dealerships, locating those dealerships through the listings on the Hummer Mailing List Home Page, or by phoning AM General at 1-800-REAL4WD. Lynch Hummer advertises a large body of pre-owned Hummers, as does Attila's Used Hummer Network. Due to the minute number of Hummers sold, there is no stable aftermarket price. Some ex-military Humvees have started to slip into the retail market, too: try Kascar, LLC.
When shopping for a used Hummer, pay careful attention to the condition of the control arm ball joints and the steering linkage, all of which wear out rapidly. Also, if the truck has CTIS, check the quick-disconnect valves at each wheel. When released, these values should disconnect the wheel from the CTIS, leaving the tire inflated; if, instead, the tire deflates, then the o-ring in the valve has stripped, necessitating that you replace the valve.
(Please don't ask me where you can get an inexpensive used Hummer, or where to get a surplus military HMMWV. Everything I know about buying a Hummer appears here. If it doesn't appear here, I don't know it.)
On-highway, a Hummer drives pretty much like a 2-ton dually diesel pickup truck. Off-highway, however, a Hummer is extremely nimble, particularly for a vehicle of its ample dimensions and great weight. Its high clearance and steep approach and departure angles let it ignore many obstacles. Every important powertrain component lies above and behind the frame, and often behind additional protective shields, minimizing the truck's vulnerability to underbody trauma. The torque biasing (think of them as limited slip) diffs that it carries both fore and aft let it operate much of the time with the center diff unlocked, allowing it to turn in a very small radius. And while Cummins fans may sneer at the small General Motors diesel, this plant has the torque where it's needed, down in the low rpm band.
Nevertheless, we're talking about a 3.5-ton, 15' x 7.5' truck. Imagine a full-sized dually: now extend the extra width of the dual rear wheels to the entire length of the truck, and you have an idea of a Hummer's dimensions. It has problems negotiating narrow forest trails, tight switchbacks, hill climbs on very loose soil, and downtown enclosed parking garages.
My Hummer boasts a consistent fuel economy rating of 11.5mpg, dropping down to 10-10.5mpg if I push the speed above 55-60mph. On the highway, it has a top speed of 71mph, or 70 if I remove the top, which increases the drag of the spare wheel the truck carries in the back. The fuel tank's 25 gallon capacity yields a working range of 250 miles per tank. To understand these numbers, think of the performance of a jeep with 5.24 gearing, then scale it to a 2-ton truck.
While I am satisfied with my truck's street performance - my previous rig was a 1978 FJ40 Toyota Land Cruiser, say no more - there are options available to improve its mileage, range, acceleration, and maximum speed. In 1994 AM General replaced my truck's 6.2L diesel with a 6.5L, and replaced the TH400 transmission with the overdrive 4L80E. 1995 saw an optional 350ci V8 gasoline engine offered, and 1996 a factory turbodiesel and auxiliary 17 gallon fuel tank option. Subsequent years have brought increasingly tame street behavior to the increasingly expensive truck sold under the Hummer name. Beyond this, various aftermarket options exist to add turbochargers, superchargers, and auxiliary fuel tanks to a Hummer.
Hummers are noisy trucks. The combination of aggressive mud tires, a flat windscreen, a diesel engine that practically sits in the driver's lap, a fabric roof and half doors, the minimal sound insulation of the '92 cabin, and steel underbody protection plates that reflect drivetrain noise up into the cabin, together yield an earsplitting din on the highway. I believe that my particular combination is about as noisy as a Hummer gets, and that's saying a lot. There are no whispered conversations in my truck: instead, the driver and his passengers bellow lustily to each other, punctuating their remarks with "What?" and "Say that again?"
Every year the new models run more quietly, as AM General adds more effective insulation. For some reason this disappoints me.
While I find my truck's highway manners acceptable, at least by tractor standards, long distance commuting is not its forte. In the face of the 18,000 miles per year of mostly mountain highway miles that my current occupations dictate, I finally broke down and bought a long-distance commuting vehicle, electing to leave the Hummer based on the farm where it belongs. Yes, I have sold out.
Many people are surprised to see the automatic transmission in a Hummer.
All Hummers, both military and civilian, use automatic transmissions. The old ones have TH400s; newer ('94 et seq) models have 4L80Es.
Modern automatic transmissions are just as stout as manual transmissions. The advantage of a manual transmission lies not in its imagined ruggedness, but in the degree of control it gives the driver over the gearing used, plus the obscenely low "granny gear" first that many manuals have. The former isn't an issue unless you're either a sports car driver or else a long-haul commercial trucker playing gear-splitting games on hills to eke out a little more fuel mileage (and, I imagine, keep yourself from going bug crazy from boredom). The latter is great for rock-crawling off-highway drivers and for vehicles just starting to move while towing extremely heavy loads.
Remember: a HMMWV was designed as a practical tool for the military. It's designed to be easy to drive, not to make its driver feel more butch (the latter being the job of AM General's marketing machine, plus the natural attraction of the Y chromosome to quasi-military toys). An automatic relieves the driver of a parameter to manage in a hostile environment. It also allows the vehicle to be driven more easily by a wounded soldier, though I don't think that was a design requirement. Too, many military recruits enter the armed forces having never learned to drive a vehicle with a manual transmission.
Practically, the automatic transmission lets the driver trick the HMMWV's stock torque-biasing axle diffs into locking by modulating the brake against the throttle. This wouldn't be possible if the driver had to keep a foot on the clutch pedal during the process. The truck would need some sort of hand brake control; even then, the driver would be juggling three controls instead of two.
When I changed my axle differentials from the Zexel-Torsen torque-sensing units to air-actuated ARB Air Lockers, I completely changed the personality of my truck. A practiced Hummer pilot would no longer recognize how my truck now drives.
Compare the drivetrain geometries of a stock Hummer and my truck.
Stock drivetrain differential geometry:
My truck's geometry:
A stock Hummer operates most of the time with its center differential unlocked, trusting to the automatic torque biasing of its axle diffs to keep its tires from spinning, seeing it through any obstacles that appear. Even on many trails it can leave its center diff unlocked. When the trail becomes so rough that the wheels lose purchase, the operator manually locks the center diff, and if necessary modulates the brake against the throttle to trick the axle diffs into locking. This gives the Hummer a degree of mobility surprising in a truck of its dimensions, and a casual "go-anywhere" capability that is very comforting always to have on hand.
In contrast, my Hummer runs all of its differentials completely open by default. This, combined with the full-time four-wheel-drive of its transfer case, leaves the Hummer nearly helpless off-highway: only one wheel needs to lose traction anywhere to leave the truck flailing helplessly, with all its torque disappearing through that stray wheel. In any off-highway situation, I now must lock the center diff, then engage the ARB air compressor, and usually will immediately lock the rear axle diff.
In exchange for this loss of casual mobility, the Hummer now handles extreme terrain more capably. The brake-throttle modulation trick of a stock Hummer is very fatiguing when used for extended periods, sacrifices a good deal of power to fighting its own brakes, exacerbates brake wear, and when sloppily used can even shear the truck's halfshafts (imagine the angular momentum of a 150 pound wheel, spinning freely in midair as the truck loses purchase: what do you think would happen should the driver suddenly hit the brake?). My completely locked Hummer now suffers none of these shortcomings.
To summarize, replacing the stock Hummer axle diffs with ARB Air Lockers gives the Hummer greater mobility at the price of much greater vulnerability when unprepared.
[TBW]
This is often the first question people ask about my truck. I must be a great disappointment to anybody expecting Thurston Howell III, or Elmer Fudd, Millionaire; perhaps on seeing me, people wonder, Hey, if that goober can drive one, they must be cheap. (My style is closer to Jethro Clampett than James Bond.) The world is full of tactless people.
Anyway: yes, Hummers are expensive; moreover, they are expensive to operate, though perhaps not for the reasons you might expect.
Compared to standard passenger rides, Hummers are expensive trucks. While I've seen used units for less than $25,000, a new Hummer nowadays starts at over $70,000 for a stripped bare model, graduating up to over $100,000 for a loaded wagon model. Once upon a time you could save a lot of money by selecting the two-seat utility model with a full-length external cargo bed and eschewing all the foofy luxe, but not any more - I guess nobody bought the bare rigs. Note that even such a stripped model will set you back far more today than I paid in 1992 for my primitive model.
Unfortunately, the purchase price haunts you long after you've signed the check. Initial price dictates insurance premiums, and in the form of depreciated value will moderate licensing fees.
Insurance quotes vary per company and the history and demography of the insured driver. Nevertheless, all other factors being equal, the high sale price of a Hummer translates to high insurance premiums. (If your insurance company gives you any nonsense about not being able to insure Hummers, find a different company. In the eyes of your insurance company, your Hummer is nothing more than a light truck or SUV, albeit a moderately expensive one.)
In Washington State, truck licensing prices seem to be pegged to the truck's GVWR as well as its depreciated value. The axles of a standard Hummer can carry 10,300 pounds at limit. As a result, I pay almost $900 a year for the privilege of licensing my truck. (This might change this year as a result of a recent state tax restructuring.)
Any vehicle that ventures off highway will require more maintenance than a pavement princess. The Hummer is no exception to this rule.
For maintenance purposes, you can think of a Hummer as a standard GM powertrain surrounded by expensive Hummer-specific components and over a score of open, lubrication-hungry joints. Powertrain maintenance is cheap, since it uses standard parts, and since diesels require little maintenance beyond changing fluids and filters. Hummer-specific maintenance, however, is a thirsty vampire that will do its best to drink you dry.
For example, take the Hummer's tires. I used to run 37x12.5R16.5 Goodyear Wrangler MTs all year long. (Try finding tire chains for that size off the shelf.) Like most good mud tires, Wrangler MTs have a brief road life, ranging from 25,000 to 30,000 miles. The standard dealership parts network wants between $550 and $650 per tire. If you go bargain hunting, you can find them at the relatively low price of $375 apiece, but you still need to have those tires mounted and balanced. Your corner tire shop is unlikely to have the tools or skills to do either. If you sport the military two piece wheels with rubber runflats, as does my truck, you're looking at a quoted rate of two hours of labor per tire to mount the tires on the wheel.
Fortunately, as the number of civilian Hummers in service grows, the maintenance story improves each year. Some economies of scale are beginning to come into play, with additional vendors of parts and accessories offering their wares, and standard part and service networks recognizing Hummers. For example, Les Schwab now performs work on split-rim Hummer wheels, mounting and balancing tires.
I perform as much of my own maintenance as possible, both for economy and for continuing surveillance of off-road damage. Any work I do takes place within the constraints of my nearly complete lack of mechanical talent, the two to three hundred miles (depending on which seasonal passes are open) that separate my Mazama garage from our Seattle house, and what until recently was my complete lack of alternate transportation. Nevertheless, I persevere, making me the redneck neighbor from hell.
Whenever the work requires skill, I cheerfully defer to professionals. Frequently this is Doug's Lynnwood Mazda/Suzuki/Hummer (yes, Mazda, Suzuki, and Hummer - it sounds like a joke, doesn't it?) in Mountlake Terrace, WA, just to the north of Seattle. That way I get a loaner car, plus the services of a diesel mechanic who knows what the hell he's doing (hi, Troy), unlike me. For tires, I turn to Les Schwab of north Seattle.
Most Hummer maintenance consists simply of checking and changing its oil (30W in the summer, 15W-40 in the winter) and ATF fluid (Dexron II), and checking the brake master cylinder (DOT5 - the violet silicone fluid). I lubricate the steering, suspension, and drivetrain every 3000 miles, or every 1000 miles (ideally...) during play season. The differentials and hubs are vented very high, and so remain clean even during extensive submarine service. The axles and hubs contain 85W-90.
The most common trauma points on my truck are the passenger-side mirror, which I destroy about every 6000 to 9000 miles, and the pins that toggle the door locks, which shear off when a tree branch slides down the top of the half-door. The CTIS shields - small metal triangles that you see in the center of each wheel, protecting the CTIS spindle and line - also occasionally eat a root or rock. Twice I've destroyed the extruded aluminum rails that mount the roof fabric. The flat windscreen is a magnet for stones and debris on the highway. I'm running my third set of balljoints, my third set of steering gear, and my third power steering pump.
The greatest hassle in the standard gauntlet of Hummer maintenance is checking the oil in the geared hub assemblies, and working on the tires and wheels. The fill plugs in the hubs are awkwardly located next to the wheels, on the inboard side, in such a manner that makes them difficult to access and check. Two of these hubs require that you remove the wheel in order to check the hub.
The wheels are a special joy all by themselves: on my truck, they consist of a two-part steel assembly bolted together with a proprietary pentagonal nut, holding a hard rubber runflat and a 37 inch mud tire. These wheels weigh 155 pounds apiece, which makes changing them a delight. Replacing the tire on the wheel requires special tools to disassemble the wheel and insert a runflat into the new tire before reassembling the wheel around the tire and runflat. (I cheerfully delegate this task to professionals.) More recent models of Hummer use a lighter, single-piece wheel, perhaps in concession to civilian drivers that don't have their own motor pool maintenance battalions.
An open-cab vehicle gets a lot of weather in its cabin. Taking my truck back to its ultra-luxurious military roots, I've modified its interior a great deal, both to withstand occasional rainfall and to increase available cabin space. Having a 1992 model gave me a head start in the minimalist race, since the earlier models of Hummer were so much less plush than more recent models.
To clean my truck, I point its nose downhill, remove accessories, cover the radios, open the floor drains, then turn a hose and scrub brush loose on the interior.
I haven't yet finished hacking my truck. (Does anybody ever?) Future planned modifications, in order of decreasing priority, include:
I drive my Hummer wherever it will fit, which is more places than you might think. Observers commonly overestimate its width. I had one ranger try to keep me off of El Camino del Diablo, citing what she described as my truck's excessive width, until I challenged her to compare my truck against her dually water truck.
In my truck, I've toured the Rubicon trail in California's Sierra Nevada mountains; the deserts of California, Arizona, and Washington; soft sand on the Oregon coast; deep snow in the Washington Cascades; and any number of jeep trails, most of which were certainly more suitable for short-wheelbase vehicles.
Most of the time, of course, I remain in Washington State. Indeed, most of my wheeling takes place in the course of ski or trail access, or simply working in the field. Here are a few of my local playgrounds.
(If you visit any of these sites in your own rig, please do everybody a favor and Tread Lightly.)
Just NW of Mt. Rainier, this area features a maze of trails for both short and long wheelbase vehicles. Most of the damage to my truck's doors took place here.
Just SW of Bremerton, this state forest has a few rutted roads worth driving.
Immediatly E of Sultan on Highway 2, the Sultan Basin Road heads past Olney Creek to Spada Lake and beyond. Cross the creeks and play in the sand pits (Reiter Pit, etc).
E of North Bend on I-90, take Lake Dorothy Road, then Middle Fork Road by the middle fork of the Snoqualmie River. A couple of mud pits are fun in the rain.
SE of Moses Lake by I-90, the Grant County ORV Area offers open sand dune driving over several square miles of Marscape. Good for playing "Rat Patrol".
The state claims this to be the world's longest beach drive. You can also drive on Ocean Shores Beach just across Grays Harbor to the N. Neither does much for me, but then, I don't care for beaches.
The entire USFS road network throughout the Mt. Baker-Snoqualmie, Wenatchee, and Okanogan National Forests becomes one big four-wheeling playground - I mean, an issue for backcountry ski access - in the winter. Snow can linger in the North Cascades through May and June.
Home base. If you see a battered tag ragtop Hummer parked at the Mazama Store, or next to an irrigation ditch in a Mazama field, that's almost certainly me. A bit further downvalley in Twisp you may encounter another tan early-model Hummer, this one being distinguishable from mine by the hardtop, the row of off-road lights above the windshield, and the lack of body damage. Anybody else is almost certainly a tourist!
I try not to take the truck to Seattle any more, as there it attracts too much attention.
Here I include a few photographic highlights, for your amusement. These are all rather old, since I don't derive as much enjoyment from wheeling for the sake of wheeling as I did in my younger years. Yes, I am old and boring.
The two kids in the picture had a dead jeep (barely visible in the upper left hand corner - look beyond the greenery), which I was busily towing when I got in a little trouble myself. My right wheels are hanging down a steep incline, concealed here by lush vegetation. Who now will rescue the rescuer?
Even more impressive than this was the sight of Kirk Glerum's 1972 Blazer, buried to the top of its doors in this pit. Unfortunately nobody thought to record that moment on film.
Other highlights of this clue-impaired run included my attempted Tarzan-style swing from a winch cable while rigging my way out of the picture here, ending in a plunge into the ice-crusted muddy water below; the unfortunate demise of a small tree unwisely chosen as Kirk's winch anchor; and our sending all of our extraction equipment off in one vehicle, only to mire all the others - with no working radios between us.
Damned right we had fun!
Here I am on a bad hair day, deflowering a brand new Hi-Lift jack.
As Hummers have the wheelbase of a Chevrolet Suburban, they're easy to high-center. Fortunately they're just as easy to free, since their differential housing, transmission linkages, and so forth all lie above the frame and behind extensive underbody protection (derived from the military mineproofing kit - I love it). It's usually more convenient to unlimber the jack and use it to tip the truck off of the obstacle than it is to rig the winch cable.
I have several pictures of my trip to the famous California Rubicon trail near the Sierra Nevada.
In a couple of these pictures you can see one front tire toeing out some ten degrees from the other tire. I had lost a grease bushing on the joint between my steering linkage and idler arm (or was it the pitman?) a couple of thousand miles before this run. The resulting wear on the joint - you could jack the truck's front end, crawl under the truck, grab the linkage, and freely shake it up and down vertically - gave my truck very sloppy steering.
This section describes the intimate anatomy of my own truck, being a 1992 civilian Hummer with a fair amount of extra rubbish bolted onto it. Other models will differ from mine in many ways.
The original military M998 Cargo-Troop Carrier was a much a lighter vehicle, with a rated GVWR of only 7700 pounds. As the United States military has pushed the HMMWV into more roles, AM General has enhanced the drivetrain and suspension to create the M1097, the M998A1, the M998A2, and further variants.
The civilian Hummer represents a divergent path of evolution. Starting in 1992 from the military M1097 Heavy Hummer variant with 12V electrics, padded seats, insulation, and a civilian light and dashboard package, it has picked up many of the subsequent military enhancements while mutating ever further down the civilian convenience and comfort axis.
Again, I'm only describing my own truck - essentially, a M1097.
My truck carries a large, heavy winch (a 12V Warn Mil-12000) slung under its front bumper, and sports extensive armor plating down the rocker panels on either side and beneath the drivetrain linkage. These skew the figures for both the weight and approach angles.
Length: 185.3 inches
Height: 72 inches
Width: 86.5 inches without mirrors
Weight: approximately 7000 pounds
GVWR: 10,300 pounds
Approach angle: 47 degrees (the winch gets in the way)
Departure angle: 37.5 degrees
Ground clearance: 16 inches
Wheelbase: 130 inches
Track width: 71.6 inches
Fuel capacity: 25 gallons
The engine is a 6.2L (379ci) Detroit Diesel Allison V-8, the old General Motors diesel of many a GMC Suburban or Jimmy. It's rated at net 150hp (gross 165hp) at 3600rpm, with 250 ft-lbs of torque at 2000rpm. The bore & stroke is 3.98x3.82in, (10.1x9.7cm) and the compression ratio 21.5:1.
The alternator is a 124A Delco-Remy 10479847, charging two 12V Delco 78-770 batteries connected in parallel.
The starter is a 12V Prestolite MMO, rated at 6hp.
The transmission is a GM 3L80 automatic, also known as the Hydramatic TH400. It's rated to handle a maximum input torque of 451 ft-lbs, well over anything that my Hummer's power plant can muster. A TH400 offers three forward gears and one reverse, with no overdrive.
The transfer case is a New Process Gear Model 242 HD AMG, with an intercooler. This is a full-time four-wheel-drive transfer case with two speeds and a manually locking differential. It differs from the NP242 used in the Jeep Cherokee and Dodge Durango in its spline count and shaft diameter, and has a maximum output torque of 2340 ft-lbs instead of the 1486 ft-lbs of the original.
AM General derived the original Hummer axles from the venerable AMC 20 axle. Their continuous torque rating was 128 ft-lbs. The stock differential uses a Zexel Torsen torque biasing design. My truck, however, runs ARB Air Lockers instead of the Torsens.
Geared hub units lie at the end of each halfshaft. This portal axle geometry provides several advantages. It allows the truck to run lighter drivetrain components and brakes to reduce weight, and keeps the axle diff housings high out of harm's way, since they need not lie in a straight line with the center of the wheel. Since the diff housing does not move, each side of the suspension can flex independently. Finally, a fixed diff eliminates a primary cause of Air Locker failure - having the air line snag or pop off the axle housing.
Transmission: 1-2.48:1; 2-1.48:1; 3-1:1 R-2.08:1
Torque converter: 1.96:1
Transfer case: L-2.72:1; H-1:1
Axle: 2.73:1
Hubs: 1.92:1
Multiply all of these together, and you get a net crawl ratio of 69.30:1. Taken by themselves, the axle and hub yield 5.24:1, which explains some of the Hummer's poor on-highway performance. (Later models of civilian Hummer use a transmission with an overdrive gear to improve this.)
The steering is by Saginaw, with a variable ratio of 13/16:1.
The brakes are by Kelsey Hayes: hydraulic actuated, four wheel inboard mounted power disc brakes with a dual reservoir master cylinder. Each rotor is 10.5 inches (26.7 cm) in diameter. The parking brake manually activates the rear service brakes.
The wheels are 12-bolt, 2-part split iron assemblies, with beadlocks and a hard rubber runflat. From November through May I run 38x12.50 R16.5 LT Interco Swamper TSL SX bias-ply mud tires, while from May through November I usually run 37x12.50 R16.5 LT Goodyear Wrangler GSA radials. These wheel and tire assemblies weigh approximately 155 pounds apiece.
A 12VDC, 1/3 HP air compressor by Thomas lies at the heart of the Hummer's OEM central tire inflation system (CTIS). [more TBW]
In my own Hummer pages, I've limited myself to describing my own truck. For more information about other civilan Hummers, military HMMWVs, or off-highway driving in general, consult the following books and web sites.
A ghost town since I deadheaded two years of stale links. I'll repopulate this someday.