Tech Tips with Steve Turchet

The Howling

I have a question about my 1963 M151 MUTT. At 50 mph, the MUTT is howling so loud I can’t hear myself think. I heard that early MUTTs had this problem, but I can’t believe that all this noise is normal. — Barry D.

Early MUTTs were notorious for howling because of poorly designed differentials. Howl may also be due to a worn transmission and/or transfer case. Another cause might be the tires.

If you trace the problem to the differentials, you might investigate later model “improved” or “silent” type differentials.

Drain First Or Pay Later

Always completely drain a vehicle’s cooling system before removing the engine’s cylinder head. If not completely drained, coolant may get into the engine oil. Even changing the oil may not get rid of it all.

When glycol antifreeze mixes with engine oil, it produces an acid that attacks bearing material. When examining rod and main bearings, if you finds dark spots this may indicate that acid has softened and eaten away at the bearing metal. The bearings should be replaced, and the lubricating oil system thoroughly cleaned to be sure no trace of antifreeze remains.

HMMWV Crack-up

FORSCOM Safety Alert

HMMWV, Cross Members, dated 2 Oct. 06

Problem:

PM Light Tactical Vehicles (LTV) has recently 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 arms 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 and 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 a 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, relative to the attached illustration, 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 of the above 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.

Deep Subject

In your article about HMMWVs (MVM, issue 103) you said it was a myth that they were parked underwater to hide them. Why not? They are waterproof vehicles. — Brent McDowl

A more accurate term would be water resistant vehicles, just as many watches are advertised as being “water resistant” as opposed to “waterproof.” The same applies to all M-series vehicles, not just HMMWVs.

Even if fitted with a fording kit, driving a vehicle under deep water is considered to be a last-resort event. It’s a very stressful ordeal for the vehicle and meant to be over as soon as possible.

Despite sealed dashboard instruments, lights and switches, as well as special gaskets and O-rings on air-cleaners, carburetors, starters and generators/alternators, the majority of seals and gaskets on M-series vehicles’ engines, transmissions, transfer cases and axles are of the conventional type. They are designed to keep oil and other fluids from leaking out, not to prevent water from leaking in. In addition, the special seals and gaskets on M-series vehicles, including the battery caps, are not intended to withstand being submerged for long periods of time. A deep-water fording kit also includes components that allow engine crankcase pressure to pressurize transmissions and transfer cases to keep water out.

If an M-series vehicle, including a HMMWV, was parked under deep water for any length of time without its engine running, you will likely find its engine, transmission, transfer case, and axles full of water when you attempt to start it.

Choke Out

My 1966 MUTT will only run well with the choke pulled out a little. I have heard that this is normal for these vehicles. Is that rue? — Dan Barker

It’s common but not normal. Many early MUTT carburetors had this defect, and a lot of MUTT owners just live with it — as did the troops who first drove them. There are replacement carburetors advertised that claim to have eliminated this problem

Send your favorite Tech Tip or question to Steve Turchet, c/o Military Vehicles Magazine, 5225 Joerns Drive, Suite 2, Stevens Point, WI 54481, USA, or e-mail john.adams-graf@fwmedia.com.