Warming up, heaters, blacking out and more in this installment of Tech Tips

Q : I’m getting ready to replace the tires on both my M416 trailers and maybe the MUTT, too. Should I buy NDT or NDCC tires? What is the difference between them? 90% of my driving will be hard-surfaced roads. Any help or suggestions would be much appreciated. — Jerry Bubolz 

A: There is a small difference in tread pattern between NDT U.S. Military tires.. The best way to see this is to look at some of the tire ads in the magazine. NDCC (Non-Directional Cross Country) may perform slightly better in soft terrain and sand... though I haven’t noticed much difference. NDT (Non-Directional Tread) is more of a compromise for highway use, but neither pattern wears well or lasts for long on the road. Nor do they grip well on wet or slip-pery pavement. I assume you want these for appearance sake on your MUTT and trailers? There’s nothing wrong with that, but you’ll probably be surprised at how fast they wear out! You will probably only get about a third of the life — if that — of conventional traction or highway-tread tires. And, of course, you know your MUTT will wear the outer sides of the tires most? Hope this helps in your decision.

In the category of little things you can do to help prolong the life of vintage vehicles, one is giving them a warm-up period of about five minutes after a cold start before driving. This allows the engine time to warm up evenly and fully circulate its oil and coolant. For jeeps and other vehicles with Dana/Spicer 18 transfer cases, put the transfer case in neutral and engage first gear in the transmission while the engine is warming. This will circulate the oil in the transfer case and pre-lube the intermediate shaft bearings prior to driving... especially beneficial in cold weather. 

Q: I want to install a G.I. issue heater in my 1959 M37. I understand that there are two kinds. One uses coolant from the engine and one burns gasoline. Which kind would be best? —TJ 

A: If you live where the winter temperature often drops below freezing, the gas-burner would probably be your best choice. For more temperate climes, the hot water type should suffice. 

Q: Can you tell me something about the blackout driving light on military vehicles? Thanks!  —Todd Mason

A: Here’s the information from Army Motors of April, 1942 when these lights were first starting to be issued. Most U.S. military tactical vehicles had already been equipped with blackout marker lights, often called “convoy lights.”

“Motor Transport veterans of the last world war and veterans of the maneuvers will raise their voices in jubilation to hear that a blackout driving beam has been developed and will be issued to all Arms end Services in the near future. A blackout driving beam! Only those who have suffered the untold hardships with trucks in pitch darkness will understand the full sweetness and significance of these words. The black nights when one man with a shielded lamp led a line of trucks like so many cattle over a broken road; when a man with one hand on the fender, guided the driver who couldn’t see his hand in front of his face. An officer discussing the beam, said, “By Jupidah, sir, there was one night in the last war I won’t ever forget - trying to steer a line of trucks into a camouflaged ammunition dump - why it was so dark in there and there was so much noise you couldn’t hear yourself think! Another time I stacked up seven vehicles at one crack when the first in line stopped for a shell hole. By God, this beam will be a blessing!’

The new light is the size of the average fog light, that is, it’s 4-3/8 inches outside diameter - and throws off a white light. There will be one to each truck, mounted up front near and slightly below the driver’s line of vision so he can look right out over it. The beam pattern of the new light is the most important and interesting thing about it. There will be no sharp beam concentrated on the road such as a spot light would throw. The beam of the new light will be a diffused light, casting illumination from 30 to 100 feet ahead of the truck like the fine spray of a hose. There’ll be no bright spot of light to attract enemy aircraft. The light is good enough to allow a line of trucks to run along safely at 20 miles-an-hour. Specifications for mounting say, ”The light shall be mounted at least 36 inches above the road surface with the beam Aimed 10 degrees below horizontal...between the center and the left hand side of the vehicle as near the driver’s line of vision as possible.” Vehicles popping off production lines will have them as soon as possible and the long-suffering lads in the field will be issued installation kits complete with light, bracket, switch and wire in the very near future. The lamp, which is made for six volts to match the six volt lighting system on your truck, is “sealed beam.” This will annoy the screwballs who would like to play around with the bulb etc. to get more juice out of it. The sealed-beam lamp is described by the engineers as a “sealed optical unit, consisting of lens, sealed filament, filament shield, reflector and hooded mask with a single horizontal slot.” You can look at picture a and figure out what they mean. There will be a small switch for the light up in the cab and the bracket of the light itself will allow the driver to make an adjustment of the beam a couple of degrees up or down.

From the flood of letters in here, it is obvious that many and many a tortured soul in the field wants to know, ‘What the heck has been holding the light up? We been needing it bad! Why didn’t somebody break down and give it to us a long time ago?” Well, that’s a good question and here’s the answer. In the first place, since the light is to be used by all the Arms and Services, the representatives of all the Arms and Services have to be satisfied that the light will do the job properly. These representatives don’t live in the woods — they are hard-headed and practical gentlemen who have been keeping a sharp eye on the progress of warfare in the last three years being as jam-packed with change and fast action as any 25 years of previous military history, they just couldn’t pin down the proper military characteristics for the light. But now...! But now by gee, we’ve got a blackout driving beam that’s eons better than any used by any army anywhere. And that’s not the whole story. Testing and experimenting with blackout driving beams is no cinch. You don’t lay on a drafting table and simply scratch one up. You go out in the great outdoors and work with airplanes, and balloons. You’ve got to have the right weather and a pitch dark night. Maybe you don’t realize it, but there’s only a couple of pitch dark nights a year, suitable for testing blackout beams. And you never know when they’re coming to enable you to have everybody around for the test. Do we sound Like we’re apologizing? We’re not; we just thought you’d like to know. Boy, there was one night out at Ft. Belvoir when a whole pack of people was rounded up for a demonstration. It was just like scheduling a picnic; as soon as everybody got there, it started to rain cats and dogs. However, the officers and men stayed with the problem, the light was satisfactorily demonstrated, and shortly afterward, adopted. The next question is, can airplanes spot the light from the air? If so, from how high (or low) can they spot it? Well, that’s the best part of it. That hood on the light prevents the enemy airplanes from seeing the full intensity beam as it shoots out from the truck. As for the reflection of the light on the road, remember what we said about the beam pattern. The light is diffused, there’s no bright patch of light for airplanes to spot. At 5,000 feet, the enemy pilot can’t see a thing. Why, if he swoops as low as a 1,000 feet, he’s gonna have to look mighty sharp to get a glimpse of the light — and even then, there’d have to be a large, bright and shiny object in the road to shoot the reflection of the beam up to him. All of which brings us to the fact that the light is not supposed to be used indiscriminately. On nights and under circumstances when enemy planes can skim low over the ground, a smart driver won’t use the light at all. On bright nights, he definitely won’t need it. But all of these things will be worked out when the light hits the field. That’ll be soon!” 

“Reliability Enhanced HMMWVs” have been specifically modified for harsh environments and increased payloads. These improvements are specific to the M1151, M1152 and M1165. Reliability Enhanced HMMWV packages include:

Q: I’m the owner of an M43. I need to repack the wheel bearings. TM 9-8030 says to use “Drift 41-D-1535-25 and Handle 41-H-1397” to remove the inner bearing cone and oil seal. Any idea where I could get such a beast? Failing that, can anyone tell me the dimensions so I can have one made up? I enjoy your magazine. —Gary Rafferty 

A: If I understand you correctly, you could always search for the proper tool, but you can use just about any suitable drift punch to drive out the bearing race and oil seal. Simply lay the wheel down with the rear oil seal underneath and use a suitable drift punch to tap the bearing race downward...evenly. This will also push out the oil seal. Tap the race alternately— first on the left then the right (or vice/versa) so it doesn’t cock sideways and jam. Likewise, you can install the race (or a new one) by tapping it back in with a drift punch, being careful not to damage the polished bearing surface. It will be apparent by feel when the race is properly seated. A wooden dowel will work as well as any special tool to install the oil seal. 

I’ve never liked skinny steering wheels, and after driving my first MV, an M38, about 1,200 miles on a trip to Death Valley, Calif., I liked them even less since my fingers got cramped. Not wanting to sissify my jeep with a one of those fancy leather steering wheel covers available in those days, I made a field modification by slitting a length of heater hose so it fit over the steering wheel’s rim, then wrapping it tightly with several layers of black electrical tape. This significantly increased the thickness of the wheel rim and gave a very comfortable grip while looking like something a soldier might have done in the field. I liked this so well that I’ve done it on almost all the vehicles I’ve owned. Try it, you might like it, too. 

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

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