Jeepology locking hubs, crossmembers and more in this installment of Tech Tips

A: Thank you, Mr. King, and thank you for your service! I don’t consider myself an expert on jeeps (or really much of anything), I just seem to have learned a little about a lot in my life. I had my own guesses about some of your questions, but I contacted a friend of mine in England who served in North Africa during WWII and here are his answers. (Oh, and he forgives you for the “limey” stuff, “yank.”) He speculates that the front bumpers were probably chopped due to the narrow and often rock-walled country lanes in the U.K. The slats, or bars, on many vehicles’ grilles were cut out in the belief this would help with engine cooling in the North African desert, though it’s very questionable if it actually did. The stars may have been inverted to distinguish British vehicles from U.S. vehicles while still showing they “were on our side.” Another explanation is that the British were peeved by having to put U.S. stars on their vehicles so they would paint them upside-down or at wonky angles. The little lights may have been for some unit identification and/or simply some commander’s (or soldier’s) whim or personalization, just as General Patton personalized his jeep. That’s the best I can do, but I’m sure other readers can furnish more information.

This is in response to your comments to the new owner of an M135. I always read your tech articles and I always learn something in spite of my over 50 years as a “shade tree” mechanic. I think you are dead-on pertaining to the front wheel lock-up in reverse (linkage adjustment). This will also happen if the truck is allowed to back down a slope while still in a forward gear. This can also be caused by locking brakes. These trucks are infamous, as is the Reo series, for locking brakes when allowed to sit idle for long periods. One problem, I think, is that the brakes are over-boosted. I have driven mine with the air tank vent open and it doesn’t have nearly as many lock-up problems. Of course, it won’t stop as well, either. I don’t have as many problems if I don’t push really hard on the brake pedal. Please tell this guy to check his brake drums, especially after driving a while. If they are too hot to touch, he needs to back off a bit on the shoe adjustment. This works for me. Where this truck really shines is when backing into very tight spaces or on delicate towing jobs where it can be eased gently without jerking the tow line. Try that with a Reo and you will either break the line or jerk the front out of the towed vehicle —Gus Causbie

A: Your friend is probably right. What happened is a fairly common occurrence on M35s that sit for long periods of time... the air-booster--or air-pack, as some call it—may lock up, either partially of fully. I saw this a lot when I worked for a government surplus dealer. I would disassemble the booster and check the condition of all the gaskets, seals and flexible parts. Also check the booster’s vent line to be sure it isn’t clogged. Getting a rebuild kit would be a good idea considering the age of your truck. Products such as WD-40 sprayed into the booster may help, but the best way I’ve found to prevent air-booster lockup on these trucks — other than actually driving them — is to start them up at least once a week and apply and release the brakes about a dozen times.

PM Light Tactical Vehicles (LTV) has learned of a problem on HMMWV vehicles with the front and rear Cross Members manufactured by Oxnard Precision Fabrication Inc. (Cage Code ODEEL). It has been found that the subject Cross Members have been fabricated incorrectly and not to the specifications of TACOM engineering. Both the material the Cross Members are made of, and the process in which the Cross Members are fabricated are incorrect. 

Testing showed that the subject Cross Members failed in the area where the lower control bolt to the Cross Member, not meeting the requirement of engineering drawings As a result of this failure, the operator could lose control of the vehicle causing possible injury/fatality to the operator and loss of the weapon system.

 Investigation by PM LTV Engineers and Metallurgical Lab test results have determined the failures are attributed to several factors related to the quality of Oxnard Precision Fabrication, Inc. provided Cross Members. Both the Cross Member and mounting brackets were not made to drawing specifications. Examination of the welding showed poor quality, insufficient penetration or completely missing in some areas.

 New production vehicles did not receive OXNARD Cross Members, this issue pertains only to spares. 

User actions: 

Place a copy of the original SOUM in the vehicle operating manual. IAW existing PMCS, after each mission, perform inspection of HMMWV underbody/ Cross Member. Pay particular attention to TM 9-2320-280-10 dated 15 Jul 04, Table 2-2. If an ODEE1 CAGE CODE is found on a Cross Member and shows noticeable cracking, bending and/or if the welding appears to be insufficient or missing the vehicle will be considered Non Mission Capable (NMC). Have the vehicle turned in at the DS/GS level for removal and replacement of the Cross Member. If the ODEE1 Cross Member does not show any defects, proceed with mission and continue to inspect after every mission IAW PCMS intervals. 

If the ODEE1 CAGE CODE is not present, further actions of this SOUM are not warranted, proceed with regular PMCS duties IAW TM 9-2320-280-10, dated 15 Jul 04. If you have a Cross Member that fits the above description please submit a PQDR via the Army Electronic Product System (AEPS) referencing TACOM SOUM 07-01.

It’s possible that these defective items were dumped on the surplus market and could end up on HMV collector’s vehicles.

The best way I’ve found to break loose a seized or “frozen” engine is to remove the head and fill the cylinders with ordinary brake fluid (not silicone, and the cheaper the better). Let it stand a few days, and the engine will almost always free up. I’ve found that brake fluid works better than Liquid Wrench, diesel fuel, kerosene, or any other methods I’ve ever heard of or tried, including on engines with cast-iron pistons. Never hammer on the tops of the pistons, even with a wooden block. Instead, remove the flywheel cover and use a stout pry bar on the flywheel teeth. Try to turn the flywheel in both directions. You’ll probably find that it will begin to move slightly at first. Then keep rocking it back and forth, and it will go a bit farther each time until the engine is finally free again. Naturally, you’ll change the oil before attempting to start the engine. Remember that brake fluid also removes paint quite well, so don’t spill it on your vehicle’s bodywork.

If your vacuum windshield wipers are getting reluctant, and you know there are no leaks in their hoses or lines — and that your double-acting fuel pump is OK — try disconnecting the hose at the wiper motor and spraying some WD-40 into the motor with the valve, or switch on. Work the motor back and forth with the hand lever or wiper arm as you do this. You should notice some improvement in the wiper action after this treatment. Also, lubricate the motor’s wiper arm shaft with a few drops of oil from time to time.

If you’re thinking about converting your 6-volt HMV to a 12-volt system, you should know that this isn’t very complicated. For one thing, 6-volt wiring and battery cables are heavier than on most 12-volt vehicles, so you don’t have to worry about that; and 12-volt generators, voltage regulators and ignition coils are readily available. You do not have to change your distributor, spark plugs and starter; indeed, most 6-volt starters will actually last longer in a system converted 12-volts, but avoid long periods of cranking. Mechanical gauges obviously don’t care what the voltage is, and most 6-volt-fuel gauges will operate on 12-volts, although step-down resistors are available. You can also install a resistor for your heater’s 6-volt blower motor. This usually leaves you with only the headlamps and light bulbs to change from 6 to 12 volts.

If you ever encounter a situation where the transmission locks up on an early model jeep, immobilizing the vehicle, one thing to check is the nut on the back of the transmission’s main shaft. This is the large nut that holds the transmission output gear in place. If the nut comes loose, the main shaft can move forward and lock up the transmission.

A properly fitted fan belt should always be flush with the top of the pulleys, or at least no more than 1/16 of an inch above them. If a belt sits too low in the pulleys, it rides on the bottom and there’s no V wedging to keep it from slipping. The result can be engine overheating, reduced generator output and rapid belt wear. On the other hand, if the belt sits too high in the pulleys, it can become unstable and twist or even jump off.

The temperature rating of thermostats (160, 180, 190, etc.) indicates the temperature at which the thermostat starts to open: It does NOT mean that your engine will necessarily maintain that temperature. Always carry a new thermostat and gasket, plus the tools to install it, when venturing far from home in your HMV.

Owners of MB, GPW, M38 or M38A1 Jeeps, or their civilian counterparts, are sometimes mystified by an odd little rhythmic skip-miss when the engine is warmed up and idling. Assuming you’ve checked all the usual things—tune-up, point setting, carb adjustment, fuel pump, possible vacuum leaks, etc.—this problem can sometimes be traced to a valve that’s set a little too tight. Adjust your valves, but try setting them about .002” wider than specs, and this little miss will usually disappear.

There has always been controversy about the proper way to store a vehicle for long periods of time and best preserve its tires. For example, some experts maintain that it should be up on blocks with its tires just touching the ground, while others say the tires should be completely in the air, and still others advise that it’s best to leave the vehicle parked normally. It’s been my experience that tires will often develop permanent flat spots if a vehicle sits for months at a time without moving. Tires will often rot where they contact with the ground or a concrete floor, as well. I see no logical reason why tires should not be completely free of the earth when a vehicle sits in storage. This should tend to keep them round because there’s no constant pressure on one specific place. This method has an added advantage, because the vehicle can be started and all its drive wheels engaged to keep axles, bearings, differentials, propeller shafts, transmissions, and transfer cases free and well lubed, all without actually moving the vehicle. Of course, your blocks must be solid and secure, and you will need to take all the necessary precautions to avoid the engine exhaust if the vehicle is stored inside a shed or garage. 

Send your favorite Tech Tip or question to Steve Turchet at military@aimmedia.com

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