PS Magazine - TB 43-PS-586
PS, The Preventative Maintenance Monthly
ISSUE 586
SEPTEMBER 2001
PS 586
SEP 01
5
PS 586
SEP 01
4
M939/A1/A2-Series Trucks.
..
Fitting Air Brake Governors
A
ir brake governors on M939-series and M939A1-series trucks can be a source of
confusion for maintenance personnel.
There have been two makers of the brake governor assembly, NSN 2530-00-854-
4457. One of the governors, FL Industries' part number (PN) N-20856-D, is no
longer available. The other assembly, Allied Signal's PN 7003-03C068537, is avail-
able—and interchangeable with FL's—
as an assembly,
but not in parts.
If you have problems interchanging these governor assemblies, ask your support
unit to add a tee, NSN 4730-00-782-5461, to the hookup. It's Item 15 in Fig 214,
TM 9-2320-272-24P-1.
Details on how to install the tee are found on Pages 3-580 through 3-583 of TM
9-2320-272-24-1.
Do not
try to mount either of these assemblies on M939A2-series trucks. They
do not have the low-pressure cutoff for CTIS that reserves air pressure for braking
in case of air system failure. You must use governor assembly, NSN 2530-01-287-
4529 (PN 106400), for A2-series vehicles.
To ensure that you get the correct assembly when ordering, add the part number
to your requisition's REMARKS block.
Tire Mounting.
..
W
hen you put a multi-piece wheel
together, make sure the tire valve
stem is 180° from the split ring gap.
The wheel is weak at the spot where
metal was removed for the valve
stem. The split ring is weak at the
gap. Put the two together at the same
place and you ask for problems. Put
‘em as far apart as possible and
you’ve done the best you can.
When you mount duals on a truck
or trailer, make sure the valve stem
of the outside wheel is 180° apart
from the valve stem of the inside
wheel. Doing this makes finding the
inside wheel stem simple.
The word’s found in TM 9-2610-
200-14
(Sep
00),
Care,
Maintenance, Repair and Inspection
of Pneumatic Tires and Inner Tubes.
Check out Para 2-4(7) for the split
ring gap/valve stem info and Para 2-
9 for the duals/stems info.
Ready? The
right place is
180
°
apart.
Make sure valve stem of outside wheel
is 180° from vavle stem of inside wheel
Make sure tire valve stem
is 180° from split ring gap
what Am
I gonna
do with
you?
I know!
add a
tee!
There’s also a
right place for
one valve stem
in relation to
another
when
wheels are
mounted as
duals on a truck
or trailer.
In the grand
circle of life,
the
difference
between right and
wrong is 180
°
.
Follow this.
..
There’s a right
place for a
tire
valve stem
in
relation to the
split ring gap
on multi-piece
wheels.
586. 04-05 (C)
8/2/01
6:00 PM
Page 1
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