This truck is an M998 High-Mobility Multipurpose Wheeled Vehicle, commonly called a HMMWV (pronounced “humvee”). This 1-1/4 ton truck replaced several different 3/4 to 1-1/4 ton trucks in use at the time of its introduction. There are many variations of this truck, including lightly-armored weapon carriers with machine guns, grenade launchers or TOW missile launchers, ambulances, communication shelter carriers, etc. There have also been other custom configurations based on the HMMWV chassis, such as the Avenger missile system. There are civilian versions of the HMMWV, called “Hummers”. My truck was used by the US Marine Corps before I bought it.
The HMMWV has been a fairly controversial truck. Every opinion I have heard about them has been either strongly positive or strongly negative. It has been criticized for being too heavy, too wide, to unreliable and to complicated. It has also been praised for being extremely maneuverable, very easy to drive, being very capable on extremely rough terrain, and being very reliable (go figure!).
At 7’1″ wide, the HMMWV is much wider than the M151 Mutt which it replaced (among other trucks). It has a very high ground clearance of 16″ under the axles, and its width helps compensate for its high center of gravity. The entire driveline is mounted very high in the body of the truck; in fact, the truck is somewhat cramped inside despite its width, because part of the engine lives between the front seats! It has 4-wheel independent suspension and full-time 4-wheel drive. Ground clearance is improved by geared hubs in each wheel, which allows the axles to enter the hubs above the centerlines of the wheels. The differentials are mounted even higher, creating the appearance of a cavernous tunnel underneath the truck. The 4-wheel disc brakes are mounted inboard at the differentials. The truck has a characteristic “sloshy” feeling when stopping because each brake are separated from its wheel by a gearbox and a driveshaft.
Although it’s a wide and heavy vehicle, the HMMWV is very easy to drive. It’s curb-to-curb turning diameter is about 11′ narrower than my 1992 Toyota 4Runner’s, allowing it to maneuver around obstacles much more easily than you would expect from a truck of its size. It has an automatic transmission and power steering. The power steering applies a lot of steering boost, allowing the driver to make tight stop-to-stop turns with a finger or two, even though the truck’s steering wheel is quite small. The sloshy feeling of the brakes takes a bit of time to get used to, but the truck is still a joy to drive right from the start.
|June 17, 1986
|69 in (5 ft 9 in, reducible to 55 in)
|180 in (15 ft)
|85 in (7 ft 1 in)
|Gross vehicle weight
|Tare: 5,200 lbs
Gross: 7,700 lbs
|Under axle: 16 in
Under chassis: 24 in
|130 in (10 ft 10 in)
|72° (47° with winch)
|292 in (24 ft 4 in)
|Front: 20 psi
Rear: 22 psi
|Model DDA 6.2 L
6.2 liter V8 diesel, liquid-cooled, naturally aspirated
|150 HP at 3,600 RPM
|260 pound-feet at 2000 RPM
|379 cu. in. (6.2 liters)
|Engine weight (dry)
|Oil pressure at idle (min)
|Oil pressure at normal operation
|190°F to 230°F
|2 qts (each of 2 diffs)
|Engine oil (crankcase only)
|Engine oil (crankcase and filter)
|1 pt (each of 4 hubs)
Front view of truck.
Left view of truck.
Right rear view of truck.
Dashboard, driver’s side.
Engine, with 100A alternator. Front of truck is towards the left.
Rear of engine, through access cover in passenger compartment.
Brandon, the guy who rents me hangar space for my 2.5-ton shop van, liked my HMMWV so much that he bought one, too! Like mine, his truck has some problems to be fixed, but I don’t think he’ll have any more trouble than I had. We think that his glow plug controller is dead, and his fan is stuck on, but his fuel injection pump doesn’t seem to have the problems that mine did.
Left side view, with 4-door soft top, cargo area cover and deep-water fording exhaust stack installed. I have not found a fording intake snorkel yet.
Left front view, with 4-door soft top and cargo area cover.
Left rear view, with 4-door soft top and cargo area cover.
Right side view, with 4-door soft top and cargo area cover. If I had the engine air intake snorkel, the intake mushroom cap, visible in front of the right side mirror, would be raised to about the top of the windshield.
A worn-out HMMWV wheel gets a new life as a portable antenna base for an AS-1729 antenna. Later, I painted the plywood part flat black.
Left front view, with antennas and intake snorkel installed.
My truck poses for a picture at Camp San Luis Obispo, at the 2000 Military Radio Collector’s Group meeting… right before going to the truck hospital for head gasket surgery.
My truck’s friends at the Santa Maria airport throw it a party after it comes out of the truck hospital with its new cylinder heads and gaskets! I couldn’t be there for the party, unfortunately, but I’ll pick it up next week. My truck is on the left. Photo courtesy of Damon, who belongs to the third truck from the left, if I’m not mistaken.
Here are some pictures of the AN/VRC-47 radio set that I installed in my truck. The large radio on the left is an RT-524A transceiver. The small radio on the right is an R-442A receiver. The lower shelf is for mounting a pair of KY-57 communications security devices (scramblers). I have the mounts and most of the cables for installing those, but I don’t have the devices themselves (yet…). I don’t yet know if KY-57 units are available on the surplus market, either intact or demilitarized.
One of the differences between early military HMMWVs like mine and civilian Hummers is that the military trucks have a separate parking brake between the rear driveshaft and the rear differential. No special tools are necessary to change the rear service brake pads in these trucks. Civilian Hummers, as well as later or upgraded military trucks, do not have the separate parking brake, and instead apply the rear service brakes through a mechanical linkage when the parking brake lever is set. They require a special tool which rotates the brake pistons while compressing them to make room for new pads.
A 32 foot string of Christmas lights is just right for the brush guard, but a 14 inch wreath is a bit small!
Here is an action shot of a HMMWV (not mine) rescuing a Mule that strayed onto deep water. The driver of the Mule, Dan Solis, made it out to the sandbar OK, but when he tried to drive back, he went into a hole and the bow wave went down the air intake and snuffed out the engine. To Dan’s credit, he had the Mule running within 45 minutes of being pulled out of the river. He said he had to do three oil changes to get all of the water out of the crankcase.
Photo courtesy of Matt Tait
A while ago, I converted my HMMWV to a 2-door cargo/troop carrier. Here it is at a military vehicle club meet in Glendale, where I bought this 3/4-ton trailer.
Photo courtesy of Brandon Kunicki
Here’s another view of the new 3/4-ton trailer.
Now, I’m converting my truck to an M1037 communications shelter. I plan to install a generator set in the 3/4-ton trailer I bought recently, and use it to power the shelter. More details about this conversion are in the modifications section.
Here are some of the modifications I have made to my truck. In general, I like to keep my truck in a correct military configuration. However, some modifications were necessary to make it street-legal, for safety, and for convenience. Wherever possible, I made these modifications completely reversible, by using existing bolt-holes for mounting, and by making wiring adapters which tap in to the wiring harness without cutting any wires. Where I added wires, I used the correct connectors, obtained from Jeff Smith, and I used silicone-rubber motor lead (SRML) wire, which is very similar to the wire used in the HMMWV’s wiring harness. I sealed all crimped connections with adhesive-lined heat-shrink tubing, and covered wires with braided polyethylene tubing where possible for abrasion resistance. The Thin-walled adhesive-lined heat-shrink tubing and braided polyethylene tubing are available from Mouser Electronics, and many types of heat-shrink tubing, with and without adhesive lining and in various wall thicknesses, are available from McMaster-Carr.
Lighted Rear License Plate Bracket
I fabricated mounting brackets out of some thick aluminum plate that I bought at a hobby shop. One bracket attaches to the top of the light housing at one end, and at the other end, it cantilevers out from the bolts which attach the U-shaped plate which protects the left rear tail-light connectors. The other bracket attaches to the rear of the light housing, and holds the license plate. I backed up the license plate with a thinner piece of aluminum. I painted all of the aluminum parts flat black. All of the hardware is either 1/4″ grade 8 hardware, or #10 stainless steel hardware, and the nuts are all locknuts.
This modification uses existing bolt holes and doesn’t require cutting the wiring harness, so it is completely reversible. People who display their truck in parades and shows may wish to use a different approach that is easier to remove for display, but I plan to use my truck as a semi-daily driver, and opted for a more secure mounting.
I did most of the metal work with a drill press and a metal-cutting bandsaw. It should be possible to fabricate a bracket like this one with hand tools, too, with a bit more effort. If you don’t have access to the correct connectors and crimper, you can cut off a wire lead and connector from a dead military headlamp. You’ll still need some sort of “Y” adapter if you don’t want to cut into your wiring harness.
I may make a bracket for the front license plate someday, but for now it’s attached to the front bumper with cable ties.
I ordered the lights and brackets used in the two-litter soft-top HMMWV ambulance, as well as the backup light switch (not cheap!) from Surplus Enterprizes, and guessed where to mount them based on a scanned picture of one of the ambulances which another collector sent to me. The mounting holes for the brackets were not already present, so I needed to drill some holes in the horizontal lip at the lower rear edge of my truck’s body.
The rubber boot around the shift lever housing should have a nipple around the neutral start switch, and another sealed nipple where the backup light switch goes. It will be necessary to remove the shift lever housing in order to get the boot off and install the switch. Be very careful, because the boot will probably be firmly stuck to the body, and it’s thin and tears easily. I tore mine and needed to replace it, and it is not cheap! It’s a big pain in the butt to remove and install the shift lever housing because of the contortions necessary to reach the lock nuts under the body through the engine access cover. I decided to ream the mounting holes in the body out and install 1/4″ rivnuts, so it will be a lot easier to remove the housing in the future. You may need to cut off the end of the nipple for the reverse switch, but my boot was the ambulance version, with the nipple end already cut off.
I had to make a separate wiring harness for the backup light switch. I did not want to cut into my wiring harness, and I wanted the blackout lighting system to continue to function properly. In ambulances, the backup lights derive power from the same electrical net that powers the horn (since the horn is shut off in blackout mode in a HMMWV), so I simply tapped my backup light power from the horn at the front of the truck. I used SRML wire, and covered it with braided polyethylene tubing. This time, instead of using a pre-made “Y” adapter, I built my own Y adapter into the end of the front wire. I spliced the two short leads with connectors to the longer lead with a special butt splice which is made for connecting a large wire to a small wire, or two wires to one wire of the same gauge. I got it from McMaster-Carr. I covered the splice with adhesive-lined heat-shrink tubing. I used the same technique to make the “Y” where the two backup light leads and the long wire from the switch join together. Each backup light has its own ground wire connected to the grounded lug on the nearest marker light. I routed the long wires along the existing wiring harness (that wasn’t easy!), and secured it to the existing harness with black UV-resistant cable ties.
For a glove box, I simply drilled two holes in the bottom of a .50 caliber ammo can, and bolted it to the floor of the truck using the two existing rivnuts where a fire extinguisher would go. I plan to mount a fire extinguisher in the alternate location under the front of the driver’s seat. I may modify the box later to make it lockable.
For a lockable trunk, I bought a Knaack Model 32 jobsite storage chest. I chose this chest because I liked the way it was made, and Knaack has good dimensional drawings on their website, including the height of the box with its lid open. That was a critical dimension when determining what box might fit in my truck. The Model 32’s lid handle lightly scrapes along the inside of the cargo cover when I open it, just because the cover sags down a bit, but I don’t think it’ll scuff the cover. I drilled small holes in the feet of the chest, and then drilled larger holes inside the floor of the chest so that I would be able to get at the smaller holes from inside the chest with a wrench. I bolted the chest to a piece of 3/4″ plywood (painted 383 green, of course!) with bolts and tee nuts, and then bolted the plywood to the floor of the truck using the existing tiedown ring mounts. I covered the large holes inside the chest with plates of thin aluminum, glued in place with silicone, to keep small stuff from getting trapped in the chest’s feet. I suppose somebody could unbolt the plywood and walk off with the chest, but it would take a while to do that, and I plan to keep that chest nice and heavy! Eventually, I plan to paint the chest 383 green, but I was in a hurry to get it installed in time for my trip to the 2000 MRCG Meeting.
I mounted the chest far enough forward to allow a spare tire to fit between it and the tailgate. Someday, I might make spare tire mounting bracket that I can attach to the chest.
Of course, I have other methods for securing my truck, but I won’t share those… :-)
Conversion to M1037 Shelter Carrier
Now, I’m converting my truck from an M998 cargo truck to an M1037 communications shelter carrier. It will carry this S-250/G shelter, containing an AN/GRC-122B radio teletype (RTTY) set.
There’s supposed to be a pair of panels which close off the rear footwells from the front seats in this configuration. I don’t have them yet, but I have located a set.
Here are some pictures with the shelter mounted on the truck. I still need to install the footwell plates and rear bumper, and realign the suspension. I’ve removed the radios to fix them. I’ll take pictures of the shelter interior after the radios are reinstalled.
|Bought the truck. While attempting to drive the truck to the truck scales to get a weight certificate, it stalled and refused to start (it started working again later). I had it towed to the hangar where I keep my M109A3 shop van, and I plan to start working on it after Christmas. It appears to have intermittent electrical and/or fuel system problems, but the engine sounds good and does not smoke.
|The electrical problem may have been caused by bad battery connections and loose alternator belts. The fuel problem will be harder to fix, because it looks like the fuel injection pump needs to be rebuilt.
|I finished replacing the fuel injection pump today. It runs! Replacing the pump is a big pain in the butt. It’s necessary to remove the intake maniford first, and it’s not easy to work on a HMMWV engine. I don’t think the truck will need too much more work to be fully road-worthy. I bought a 4-passenger top kit and cargo area cover, and the mirrors should be here in a few days. I picked up a take-off fording exhaust stack, but I still need an intake snorkel.
|The truck seems to be running pretty well now. I gave it a bath, installed the mirrors and wiper arms, bolted on a beat-up surplus fording exhaust stack, and began working on installing the soft top. The connection between the battery current shunt and the alternator/chassis ground cable was loose, and made some pretty sparks. Monte Bowe’s truck had the same loose connection, so maybe it’s a common problem. I can’t finish installing the soft top until I get some replacement wellnuts for the windshield frame and B pillar. I’ll also do without the cargo area cover for a while, until I fabricate the metal plates which reinforce the body around the mounting brackets.
|After servicing the parking brake, I took my first “real” on-road trip in my HMMWV late tonight (that short first trip out of the auction house yard, followed by a stall and a tow, doesn’t count!). I just went down to the nearest gas station, hopped on the freeway briefly, and returned to the hangar (about 10 miles round trip), but I’m pretty happy that the engine ran and nothing important fell off. I think it’s just because of the tread pattern on the military tires I’m running, but the truck really wants to wander around on rough pavement.
|The HMMWV makes it home! My M998 finally made the 30-mile-long trip home from the hangar where I’ve been working on it for the last month. I started around 9:30 PM, taking a chance that the darkness wouldn’t be a problem in order to avoid heavy traffic. Most of the trip was on a very hilly freeway through an uninhabited stretch of mountains. At least one wheel seems to be badly out of balance, so I had to keep my speed under 55 MPH so the truck wouldn’t get too squirrelly. Several times on uphill segments, the engine started making a loudroaring sound. I think it was probably the fan turning on, but the jury’s still out. There was a plastic-burning smell, and I have not found a cause for it yet (maybe a slipping belt?). I pulled over three times at call boxes to count the wheels, look for smoke, see if any of the tires seemed too hot, let the engine cool a bit, etc. Two of my stops were right before toll booths, so at least I was in lighted areas those times. All in all, it was an exciting trip!Upon arriving home, I managed to get the truck into my garage without removing the fording exhaust stack or hitting any walls… I was a bit surprised that I actually shoehorned it in! I did need to detach the garage door opener carriage to get the door open far enough to clear the exhaust stack. My downstairs bedroom (and future radio room) has been extended into the garage, so there’s really only room for one vehicle… and a HMMWV is a bit more than one vehicle!Inspecting the truck after my arrival, I discovered that one of the brand new grade-8 locknuts I used to re-fasten the exhaust crossover pipe cracked in half… that’s a puzzler, because I even torqued them to spec with a torque wrench. I noticed a bubble in the plating on the lower metal coolant pipe (where the drain cock is). Light finger pressure crunched it, and a few drops of bright green coolant came out! Eeeek! The radiator hoses feel pretty crunchy, so I think I ought to just replace that pipe (I bet it isn’t cheap!), all of the radiator hoses and the thermostat, and flush the radiator. I also want to test the fan to make sure its clutch works right. I plan to disassemble all of the wheels, remove the run-flats, replace tires as necessary, and have them balanced. It’ll probably be a while before my truck takes its next trip… between the bad smell and the rust-through I found on that coolant pipe, I think my truck was lucky to make the whole trip under its own power!
I bet my neighbors will freak when they see that HMMWV in my garage… hee hee hee! :-)
|I finished installing the cargo area cover tonight. The truck looks pretty sharp, now! The right rear eyelet on the rear curtain won’t stretch far enough to go over its footman loop, so I may need to move the loop over a half inch or so. I think that the burning plastic smell that showed up on the drive home was caused by a plastic label I found on the side of the muffler (which appears to have been replaced). I probably hadn’t gotten the exhaust system hot enough to cook it before. Folks tell me that the loudroar is normal, and is caused by the engine cooling fan, which is controlled by a hydraulic clutch and a solenoid valve.Yes, my neighbors did, in fact, freak. :-)
|While lubing the chassis, I discovered that the bolt holding the left radius rod (like a tie rod, but sets the toe-out of the rear wheels) to the chassis was very loose, allowing the rod to rattle around. After jacking up the left rear wheel, I found that I could easily “steer” it about 1/2″. Yikes! That would sure explain why the truck wanted to wander all over the place on the trip home last week. It would also explain why the left rear tire is worn out, while the other three look pretty good. I tightened the bolt back up, and I guess I’ll be learning how to do a 4-wheel alignment soon! On a brighter note, all four pairs of ball joints seem to be OK.
|This afternoon, I finished disassembling, inspecting and remounting the right rear tire and both front tires. I wanted to remove the runflats, and also inspect the tires for runflat damage, so I would know how many new tires I will need. The left rear tire needs to be replaced; it’s worn out by the alignment problem, and it has too much dry rot for use as a spare. I didn’t bother removing it; I’ll do that when I get a replacement. The other three tires look OK on the inside, but the front right tire has a 1/16″ diameter, 3/16″ deep hole in the sidewall. The hole doesn’t go all the way through, and doesn’t leak, but that tire might want to become the spare, anyway. Remaining tasks:
|It’s been a while since I updated the status page, but I’ve been busy. In no particular order:
|I decided to take a few days of vacation to work on my truck. Today, I picked up a couple of new tires I ordered ($300 each… Ouch!), installed a new lower coolant pipe, and flushed the radiator. I backed the truck out of the garage to run the engine right as the neighbors’ kids were getting home from school. My house was very popular today! I let the kids climb over the truck, because I knew they’d never leave me alone otherwise. I can go back to being grumpy tomorrow.
|I’ve been busy in the last few days. I had planned to replace the outer end of the left radius rod (the same rod which was loose before, and thus would need to be adjusted), because its dust boot was torn wide open. I was unable to get it to budge in the adjuster sleeve. After hours of torching, Liquid Wrenching, hammering and cussing, I managed to get the other end to turn about a half rotation… I gave up, and had George Pretty [no longer in the HMMWV parts business]express me a whole new rod (I’d rather waste my money than my blood and skin!), which I received this morning. I put plenty of anti-seize on its threads, and it was easy to turn by hand after installation. Ironically, it was almost the correct length when I installed it, and the right radius rod needed the most adjustment. Luckily, I got its sleeve to turn with some Liquid Wrench, a bit of rapping with a hammer, and all of my weight on a pipe wrench.I finished the alignment today, and over the last few days I’ve also replaced both front tires, installed the radio tray, mounts, antenna bases, and wiring, re-installed the transmission hump padding, bolted an ammo box to some existing rivnuts on the hump between the front seats for use as a glove box, removed the cargo bulkhead (it turns out that it interferes with the rear seat transmission hump padding), changed the fluids in both differentials and the remaining hub gearbox, and made lots of other minor fixes. I think that I’ll just need to balance the wheels to get the truck fully road-worthy! I hope I have enough energy left to do that tomorrow.While test-driving my truck today (for the first time in months!), I noticed that there seems to be a lot of gear noise coming from the back of the truck… I hope that’s normal! I sure got some funny looks driving that HMMWV around the neighborhood! (Hee-Hee!)
Future projects include installation of backup lights (waiting on connectors and a crimper), installation of the radios (waiting on the radios and one antenna whip element… the rest is all there, and they should just drop in the mounts), fabrication of a front license plate bracket (cable ties for now!), looking into a very slow leak from around the transmission, mounting a spare tire (I’ve put that off until I have a pro take a look at the non-penetrating sidewall hole in the tire I plan to use, and tell me whether it should be patched or left alone), and fixing some butchered and/or decayed wiring around the alternator. I think all of the major stuff is almost out of the way, other than any new bugs which might get shaken out during the next 500 miles or so.
|I didn’t have enough strength left to balance the wheels today, so I changed the transfer case fluid and the transmission fluid and filter instead. That was a messy job! I’ve been told by an experienced HMMWV rebuilder that my rear-end noise is normal, so I guess my truck is fully road-worthy, except for needing its wheels balanced. I’ll do that soon, but I don’t see why I shouldn’t drive it to work tomorrow. WOO-HOO!! I took it for a 10-mile test drive this evening, and it seems to be running well.
|Since the last entry, I’ve finished installing the radio (an AN/VRC-47, a member of the VRC-12 series of radio sets, and consisting of an RT-524A transceiver and an R-442 auxiliary receiver), installed backup lights, and balanced the wheels. I tried to mount the spare tire after the tire shop looked at it and determined that the sidewall hole didn’t go all the way to the cords. Unfortunately, the surplus wheel I bought a while back failed the feeler gauge test. I recycled it as a portable antenna base. To secure my vehicle, I decided to use a Pit Bull Tire Lock. Its jaws didn’t open quite far enough to go around those big HMMWV tires, but I made it work by cutting off the protruding part of the steel core from the inner (larger) jaw. The backup lights are from an M1035 HMMWV two-litter soft-top ambulance. They’re not correct on an M998, but I think they make the truck safer to drive, and at least they’re from a HMMWV. I tapped power for them from the horn, so that the backup lights will only operate when the lighting system is turned on (just like the HMMWVs which are supposed to have them). I’ll add new pictures showing the antennas, radios, intake snorkle and backup lights someday, when I get around to it. My truck seems to be running great!
|Last Thursday, I drove my HMMWV up to the annual Military Radio Collector’s Group meeting in San Luis Obispo, CA, about 250 miles north of my home. It was a lot of fun, and I happened to meet many other HMMWV collectors. Unfortunately, it looks like my truck developed a head gasket leak, so it didn’t make it back home. I had it towed to the workshop of Bob, an expert HMMWV rebuilder in nearby Santa Maria, CA (about 200 miles north of my home), and he’s agreed to take on the job of replacing the head gaskets. Since replacing the fuel injection pump is about 3/4 of the same job as replacing head gaskets, I know that I could do the job myself… and I also know that I don’t want to! :-) ALT=”smiley”> Bob says that the noise coming from my rear end is not normal. That’s both good and bad… it means that I’ll be doing some more repair work once my head gaskets are replaced and I drive my truck back home, but it also means that I can make that !@^* noise go away! On the brighter side, even with a leaking head gasket, my truck still starts more easily and runs better than most of the other HMMWVs I’ve seen. I’m crossing my fingers that I’m just working the last few kinks out of it now.
|My truck’s out of the truck hospital, with a new pair of (surplus) cylinder heads and new head gaskets! I’ll drive up with a friend of mine next weekend to pick it up. A few of its friends threw it a party to celebrate it’s successful recovery. Once it comes home, it’ll need a bit of rear differential surgery, but it’s getting pretty close to being in top health. While I have the gearbox out, I might as well service the rear CV joints and replace their boots. I plan to do the same to the front, but I figure I’ll need to drive it a bit more first once I get the rear end all fixed up. I can’t wait to get my truck back home! While I’m up in Santa Maria, I’ll definitely make the trip up to Jocko’s for some of the best steaks in the world.
|I drove my truck home last weekend. It’s great to finally have it back in my own garage! It runs great at speed, but it now smokes and runs roughly at idle, especially when cold. I hope that new problem won’t be hard to fix. It has developed a power steering pump leak, and I need to replace one of the alternator brackets. I plan to do both of those things before I do anything else. Then, I need to flush the cooling system and refill it with the right antifreeze mixture, and then get to work on the rear diff. After that, I want to install the 3-point seatbelt mod (that’s neither cheap nor easy!), and then work on lots of other little things. It never ends… :-) I replaced the shorted windshield washer pump with a NOS replacement, but I haven’t done anything else to it. I think I’ll let it sit in the garage for a while before I get started, while I work on other neglected projects. I’m kinda sick of dumping time and money into it for now, so it’s time to take a little break! I’m sure it won’t be too long before I’m swinging wrenches at it again.
|I ignored my HMMWV for a spell, while I worked on my commercial driver’s license for my 2.5-ton van (and that’s still in progress!), but I’ve finally started working on it again. I pulled out the alternator a couple weeks ago, repainted it because of some surface rust, and replaced the missing fan guard. That wasn’t much work, but today I got serious, pulling out the power steering pump and cleaning and rebuilding it. Its seals were all shot, but it looks OK otherwise. The seals kit is pretty cheap, but it takes a fair amount of labor to pull it out, clean it up, and replace the seals. Next time I work on it, I’ll install the power steering pump and alternator, and fix some ratty alternator wiring. My truck should be running again then, so I can flush the cooling system and go get some fuel… then it goes back up on jack stands so I can rebuild the rear diff! I haven’t decided whether I’ll do that myself or take it to a diff shop. As long as I have it out, I’ll probably replace the rear CV boots and check out the rear CV joints.
|I got my truck back together today, and flushed the cooling system. It felt good to drive it again after a month, but I don’t plan to drive it much more until I rebuild the rear diff. While flushing the cooling system, I discovered that both of the 3/8″ hoses which run from the high spots on the radiator and the engine to the surge tank were plugged up at the surge tank nipples. These hoses let air escape from the radiator and engine and go to the surge tank, rather than getting trapped. In the “rinse” cycle of the chemical flush, I got about a mile from home and then my temperature shot up to 240°F. I think there was a big pocket of trapped air in the radiator, and then when my thermostat opened up it burped up to the surge tank and the water level in the engine dropped. Now that they’re clear, I can get the coolant level right on the first try. The next step is to rebuild the rear diff, but I might wait a while before I start spending time and money on that.
|Well, I finally fixed that rear diff, and my truck is fully road-worthy again! I took the diff in to the local Hummer shop to have it repaired. One of the bearings on the input shaft broke, but the gears were all still OK. I had them replace all of the seals and bearings. I reinstalled the diff a couple days ago, and test-drove the truck this evening. No more ear-plugs! Woo-hoo!It’s still hard to carry on a conversation in this truck, but now that the rear diff isn’t howling any more, I no longer need to wear hearing protection in when I drive it.I guess the next major task is to install the 3-point seat belt modification. There are a few other minor things to do to it, too, but the truck is basically fully road-worthy now!
|I’ve suspected for a while that my brake light switch wasn’t working quite right. I temporarily installed an indicator light so that I could see when my brake lights come on while I drive the truck. Due to pitted contacts (I’m guessing), I cannot adjust the switch to turn the lights on fully with light brake pedal pressure, but turn them off when I release the pedal. Last weekend, I made a bracket out of some hunks of metal and temporarily installed a snap-action lever switch in place of the original switch. It works well, but isn’t waterproof, and isn’t very sturdy. I have the right switch on order. I’ll also replace the plastic bushings on the brake pedal mounts, because one is broken. While I’m at it, my truck needs a new hand throttle cable, too.Today, the seat belt latch at the driver’s position finally gave up the ghost. The other three aren’t far behind, judging by the condition of their plastic parts. My parts dealer doesn’t have the 3-point upgrade kit for the front seat in stock right now, so I just temporarily replaced the driver’s seatbelt with a cheap non-retracting belt from Pep Boys.
|My truck still smokes and rattles a bit more than I like when started cold, but otherwise it’s running really well. I’ll check the glow plugs a bit more carefully soon. If that’s not the cause, then I’ll just live with the smoke. I replaced the bad brake pedal switch. I thought one of the brake pedal bushings was broken because of some play in the pedal, but it turns out that the play is just because the hole in the pedal bracket is a bit larger than the pivot pin. I replaced the bushings anyway as long as I had it apart. I also discovered that my hand throttle cable wasn’t in such bad shape, after all, so I guess I didn’t need to replace it after all, but as long as I bought a new one anyway… I need to stop being so picky and just drive the @^$! thing! :-)I got a surplus brush guard from eBay recently, and I installed it tonight. The guard and one of its brackets are a bit bent, but I figure that give it character. The guard is one of those wimpy early-model military ones, but it should work out just fine since I don’t plan to do any really serious off-roading. No pictures yet, so you’ll need to wait until I have another reason to take a new picture of the truck if you want to see it. :-) I also got a pioneer tool rack there, but I’ll leave it off the truck until I have some tools for it.
|Well, it looks like my brand new brake light switch has failed just like the last one, so the brake light won’t come on unless I put a lot of pressure on the brake pedal… much more than I use in a normal stop. If I readjust it to turn on with light pressure, then it won’t reliably turn back off. I believe that this is a design flaw. A rotary switch should not be used in that application, because the edges of the contacts will arc, heat up, and get pitted when the brakes are lightly applied, thus creating a high-resistance area between “on” and “off”. I’ve put that home-made bracket and snap-action switch back in. I’d like to replace it with something a bit less chees someday.I also installed my surplus military GPS receiver and its external antenna recently. The antenna is on a home-made bracket mounted behind the snorkle support bracket, and the GPS receiver hangs from the roof just to the right of the driver’s seat. While I was at it, I added a dome light to the bracket that I made to mount the receiver. That’s a lot nicer than fumbling for a flashlight in the dark. Surprisingly, this installation required no holes or other permanent modifications.
|I’m converting my truck to an M1037 shelter carrier. I have an S-250/G shelter containing an AN/GRC-122B radio teletype set which will be mounted on the back of the truck. This conversion includes replacing the rear suspension with heavier-duty components, mounting a special frame in the bed, relocating the tailgate to the end of that frame, and other modifications.