PS Magazine - TB 43-PS-682
PS, The Preventative Maintenance Monthly
ISSUE 682
SEPTEMBER 2009
16
PS 682
SEP 09
17
PS 682
SEP 09
Dear Half-Mast,
I heard that some of the older oil pressure switches on FMTVs have been
replaced with new ones. Can you tell me what the deal is with this?
SSG N.O.C.
Word from the Feld is that HEMTT
users have found transmission oil blows
out of the vent at startup. That’s a sign
that the oil level could be too high.
OverFlling is the likely reason for
blowoff. That’s why making sure the oil
levels are within the limits spelled out
on Page 2-50 of TM 9-2320-279-10-1 is
important.
If that doesn’t solve your problem, you
may need to back off on the Fll level.
Your oil level has to be closer to the COLD
end of the dipstick than the HOT.
When
you
make
your
after
operation check described in the
-10-1 TM, maintain an oil level
between the letters “L” and “D”
in
COLD.
Remember,
this
after
operation check is made with the
parking brake set, transmission in
neutral, engine running, and with a
hot transmission (over 160°±).
The steps listed above are the
only
approved solution whenever you Fnd blowoff.
Making the dipstick tube longer won’t solve the problem of getting the proper fluid level
in the transmission.
Of course, if your HEMTT doesn’t blow transmission oil and registers proper (TM-
prescribed) levels on the dipstick, you’re good. So keep your oil level right where it is.
Dear Sergeant N.O.C.,
Can do! There are three different oil pressure switches used. Which pressure
switch is used depends on which model FMTV you have. The newer switches have
an improved diaphragm made out of a more durable material.
Here’s what you need to know:
Basic FMTVs with Caterpillar 3116 engines use the analog style 12 psi-activated
pressure switch, NSN 5930-01-528-7523, PN 12419189-004. This is used on trucks
with serial numbers below 11,438. It replaces NSN 5930-01-384-5419 shown as
Item 6 in Fig 68 of TM 9-2320-365-24P.
FMTV -A1 models with Caterpillar 3126 engines use the digital style 6 psi-
activated pressure switch, NSN 5930-01-515-6564, PN 12419189-003. This is used
on trucks within the serial range of 11,438-25,248.
Finally, FMTV -A1 models with Caterpillar C7 engines use a digital style
pressure switch, NSN 6620-01-524-9112, PN 161-1705. That’s used on trucks with
serial numbers higher than 100,000. (There are no trucks within the serial range of
25,249-99,999.)
And that’s the deal for FMTV oil pressure switch switches.
±MTVs…
Oil Pressure SwitCh SwitChes
HEMTT…
transmission oil check challenge
See if transmission oil level
matches the TM’s guidance
Keep oil level between “L” & “D” in COLD
having problems
with your hemtt
transmission’s
oil level check?
you’re
not
alone.
cause it’s
time to switch
my old oil
pressure
switch…
…but he has
no idea which
new switch
to switch it
with!
why is he
thinking
so hard?
682.16-17.indd
1-2
7/21/09
6:12:43 PM
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