By Steve Turchet
HMMWV CABLE CARE
HMMWVs with serial numbers beginning with 44825 may develop a parking brake cable problem. The cable bracket design was changed to solve this problem (but of course if you own a surplus HMMWV that probably doesn’t help). The problem is the parking brake cable being crushed or chafed by the lower control arm.
Check your vehicle to see if this is happening. If so, you may want to order the new and improved cable bracket, or make a new bracket at home. At the very least, the parking brake cable should be wrapped with rubber tape or covered with a piece of hose to prevent chafing.
I am having transfer case problems with my 1991 HMMWV that I bought a few months ago. When I use the lock for driving in sand it is very hard to get it unlocked again. What’s wrong?—TK
Try backing up a few feet before unlocking the transfer case. If that works, there is probably nothing wrong. This is the same concept as backing up a little before unlocking front axle hubs on other vehicles… it releases the built-up tension in the drive train. As you probably know, never use lock when operating your HMMWV on dry hard surfaces. Here are a few extra tips from the military manual:
Select the proper transmission and transfer case gear ranges. “D” (Drive) and “H” (High Range) are used for most situations. The HMMWV must be stopped and the transmission placed in “N” before shifting the transfer lever.
Do not shift into any lower gear than necessary.
Use “H/L” (High Lock Range) or “L” (Low Range) only when absolutely required by terrain, weather, or road conditions.
On steep grades with hard surfaces and good traction, before starting up the hill, shift the transfer case to “L” (Low Range) and the transmission to “2” (second) or “1” (first), depending on the steepness of the grade.
Keep the engine operating at a constant, moderate speed to slow down or speed up quickly without changing gears.
The engine works at its best in the mid-RPM range. Maximum torque is attained at 2000 RPM.
Attempt to keep the vehicle’s wheels from spinning. If the wheels start to spin, ease off the accelerator until traction is regained.
I have a 1993 M998 HMMVW and have always had trouble with the windshield wipers. The motor seems to run OK, but one of the wiper arms will sometimes stop moving, especially when wiping snow.— R. Mendoza
This is a common problem on early model HMMWVs. The early style wiper arm pivot had a round shaft, and the wiper arm splined base was pressed onto this shaft. Over time, and especially if wiping mud or snow, the arm mount would come loose from the shaft.
At first, this usually results in the arm still moving sometimes, but eventually it will stop moving entirely. The new style pivot has a square shaft, which eliminates this problem. It’s a fairly simple job to replace the old style pivot with a new one.
GREEN BABY POO?
Many jeep and M37 owners are puzzled by a sort of green “baby-poo” that accumulates in their engines’ oil-filler pipes. This is caused by moisture in the crankcase, which usually happens because the engine is either running too cold or never gets fully warmed up… as with vehicles that aren’t driven a lot.
Water in the oil creates acids that eat bearings and etch metal, so the best thing to do is take your vehicle for a nice long drive once a week. Just starting it up and running it for a while at idle isn’t good enough, especially during cold weather.
If you can’t drive your vehicle enough to warm it up, it’s sometimes better not to start it all. At the very least, change your engine oil frequently.
SPIT AND POLISH
Automobile polishing compound will quickly clean your windshield and window glass of old crusted stuff, bug splats and paint overspray. It also works great on mirrors, reflectors, and head and tail light lenses. Car wax will brighten and preserve plastic lenses.
AN OLD TRICK
My grandfather had a Model AA truck and he told me he got better gas mileage on the highway by reaching up and pulling the vacuum line off the windshield wiper. Would this work on my ‘44 Willys MB?—Stan
Probably. But, did your grandfather also warn you this trick can burn valves in the engine? This will probably cost a lot more in repairs than what you might save on gas!
Although many people think they should use heavier oil, such as 40 or even 50 weight, in a well worn HMV engine to compensate for loose bearings and piston rings, this old-time practice may actually accelerate wear because the oil is too heavy to properly lubricate many parts, or be splashed up onto the pistons. The use of heavy oils may also rob an engine of power and decrease fuel mileage. You might find that a good quality 30 weight, or even a multi grade, such as 20-40w, will make your old engine perform better and last longer.
KEEP YOUR HMMWV COOL
HMMWVs have what is called a “cooling stack,” which consists of the power steering cooler, the engine oil cooler, and the engine’s radiator. Over time, dust, dirt and debris such as leaves, grass and bugs accumulate in the cooling stack, especially if the vehicle is used off-road. This reduces cooling efficiency and may result in an overheating engine.
For an HMMWV in daily use, check and clean the cooling stack about once a year. Check it more often, if the vehicle is used off-road.
First, move the power steering cooler out of the way. Then remove the screws that hold the engine oil cooler to the radiator. Carefully insert small wooden blocks (pieces of 2 X 4 work fine) at each corner of the oil cooler to support it above the radiator. Then clean between the oil cooler and radiator with low pressure air or low pressure water. You should also check for bent fins on the radiator and oil cooler, and carefully straighten them if necessary.
A CLASSIC CASE
I have a 1952 Willys M38A1. I have had this jeep for over 25 years. I use it only in the spring, summer and early fall. My problem and question is how do I adjust the toe-in on this vehicle? I believe it is the toe-in adjustment that is causing the strong shimmy on occasion when applying brakes or hitting a pothole. I have replaced all the tie rod ends, adjusted the drag link, steering box adjustment, all by specs in the M38A1 service manual. I am familiar with vehicle repairs as I have over 40 years experience in automobile and heavy equipment repair. I guess my main problem is getting the toe-in correct. When I adjusted it, it seemed to improve, however, every so often I hit a pothole and it will vibrate like hell till I bring it to a stop.
Is there an easy way to mark the front tires and measure the toe-in? As you know, the front part of the tires are easy to access. Any help you could give me on this problem will be greatly appreciated.—Ken Baker
Sounds like you have a classic case of front-end shimmy. The simple answer is, toe-in is adjusted on an M38A1 (and all other jeeps with two-piece tie-rods) by shortening or lengthening the rods by screwing in or screwing out the ends. While the basic procedure and measurements should be in your manual, these apply to a new jeep in 1953… not to a vehicle that’s now over 60 years old.
The best place to start is to read my article on curing front-end shimmy (MVM No. 91) and follow ALL THE STEPS IN ORDER IN WHICH THEY ARE WRITTEN.
You mentioned you’ve replaced many parts and made some adjustments… but have you checked the bell-crank bushings for wear? If the bell-crank is loose and sloppy, this will allow your jeep to shimmy no matter how many other new parts you’ve installed or what adjustments you make. To check the bell-crank, jack the vehicle’s front wheels off the ground and have someone turn the steering wheel all the way from one side to the other and back again while you watch the bell-crank. If it wobbles even slightly and/or moves up and down, the bushing is worn and must be replaced.
There are bell-crank repair kits offered from many sources. If the bushings are worn, this problem MUST be fixed before you make any other adjustments, or you will probably never cure your jeep of shimmy.
WET OR DRY?
Thank you for your helpful articles and technical tips. I have an MB, an M38, and an M151. Many of your articles have been useful to keep them going.
In a recent issue, there was an article about replacing the oil bath air cleaner on jeeps and MUTTs with a dry element. I read it several times but I can’t see any advantage to doing this except it makes servicing the air cleaner not so messy. I would like to get your opinion on this subject.—Ray Fillmore
You’re right. About the only advantage to converting a wet type oil bath air cleaner to a dry element is making air cleaner service less messy. The disadvantages: you are now tied into the cycle of buy-and-consume. Instead of being able to service your air cleaner anytime and anywhere by simply washing it with solvent and adding new engine oil, you must now buy a new element. What if those elements are no longer made in the future?
I can’t see the point of switching from an air cleaner I can service myself with stuff I already have to a unit I now have to buy something to service. While in some cases, dry element air cleaners may filter a little better than wet types, that seems irrelevant for HMVs, since most are not driven very much, or used extensively off-road. And of course the vehicle is no longer original, regardless of whether or not the modification is visible.
I once worked for an aircraft scrapping company in Arizona that had several cranes and other heavy equipment, some of which used dry type air cleaners. The dusty environment required frequent air cleaner service, and the company’s owner pitched fits at the cost of the large dry elements. And while they could be washed several times by a company that specialized in that process, it was still expensive, and the equipment was either off-line or operating without air cleaners while the elements were being washed. I went to a truck wrecking yard and bought oil bath air cleaners, installed them on all the equipment, and the owner was all smiles at the reduced cost of maintenance.
DATA PLATE DILEMMAS
For what it’s worth, here’s my experience buying an HMV that had a “recycled” data plate.
I bought my first M37 in 1976 from a surplus dealer in Tucson, Arizona. He told me up front it was actually a 1958, but he’d switched the glove box door with data plate from a 1966 basket-case because he’d bought the ‘58 off a ranch with no title.
The complication was that, at the time, a 1966 vehicle was required to pass a smog inspection to license. This was done at the DMV in Tucson with the vehicle on a dynometer (rear wheels on rollers in the floor). A probe was inserted up the exhaust pipe, and emissions were first checked at engine idle, then again after the vehicle was run up to 60 mph. The fun began right away! The truck had been sitting out in the desert for years, and looked it. The driver’s seat was bare springs, and the inspector didn’t even want to get in! But his boss, behind a glass window, ordered him to. The truck had its stock exhaust system with a sharp bend in the tail pipe where it came out behind the right rear wheel, and a flange for a deep water fording kit snorkel. The probe wouldn’t go all the way in!
By this time, other inspectors had gathered to watch. If you’ve ever heard a stock M37 doing 60 mph, you know the engine sounds like it’s going to explode. The probe kept falling out of the tail pipe! After three tries, with the other inspectors holding their hands over their ears and mockingly duck for cover every time the engine wound up, the guy the behind the glass snapped over the PA system, “PASS IT AND GET IT OUT OF HERE!” So much for the official process.