PS Magazine - TB 43-PS-627

PS, The Preventative Maintenance Monthly

ISSUE 627

FEBRUARY 2005
PS Magazine - TB 43-PS-627 - Page 8 of 33
M915A3 Axle Breather
Use NSN 5340-01-355-3115 to get a curved axle breather for the M915A3 tractor truck. This
new breather stops oil blow-by and replaces the NSN shown as Item 4, Figs 140 and 141 of
TM 9-2320-302-24P.
FMTV Ring Mount Cover
Use NSN 2540-00-909-3745 to get a canvas cover for the M66 ring mount on the MTV (5-ton
models). NSN 1005-00-707-0725 gets the cover for the LMTV (21/2-ton). Use these covers to
protect the ring mount from rain, dust, dirt and sand.
PS 627
FEB 05
12
M977-Series HEMTTs…
Dear Half-Mast,
We have some concerns about MWO 9-2320-279-20-9,
Installation
Instructions for Bolt Together Wheels for the M977-series HEMTTs.
After installing the bolt-together wheels, we’ve found that there are
zero
stud threads showing past the lug nuts after correct torque is applied.
Because of that, it’s obvious that the studs and wheel nuts do not meet
the criteria spelled out in TB 43-0218,
Inspection, Use and Tightening
of Metal Fasteners Used on Tank-Automotive Equipment.
Para 7b on Page 6 says, “In all installations, bolts, studs and screws
must extend through the nut at least a length equivalent to two complete
threads. This applies to both self-locking and plain nuts.”
Is there a longer wheel stud that we should be using when applying this
MWO? Or are the current studs OK, even with no threads showing?
MSG J.J.K.
Master Sergeant J.J.K.,
Good questions! in this particular case, however, TACOM says the criteria from
TB 43-0218
does not
apply.
The key to any lug nut/stud com-
bination is not the visual check, but
the requirements for clamping force
and torque retention. It doesn’t mat-
ter how many threads protrude out-
side the lug if the clamping force
cannot be met or the lug will not
hold the torque.
To ensure proper torque reten-
tion, the lug nut height must be at
least 80% of the stud’s diameter.
The current HEMTT design exceeds
this requirement, so there’s no need
for the studs to extend past the lug
nuts.
Before the MWO was released,
TACOM put HEMTTs through mul-
tiple tests, including several brake,
shock and vibration tests and more
than 25,000 test miles. There were
no incidents of lug nuts loosening
during these tests.
Today, more than 2,000 HEMTTs
are currently operating with the
bolt-together wheel
configuration with no
problems reported.
No stud threads will extend past
lug nuts on bolt-together wheels
hey!
no threads
showing…
no
problemo!
but I did
everything
the mwo said!
what do we
do
now?
there are
no
threads showing
on the lugs of my
new bolt-together
wheels!
I think
we got a
problem
here,
buddy!
Missing
Threads
Not
a Problem
627.12-13(C)
12/24/04
2:36 PM
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