PS Magazine - TB 43-PS-628
PS, The Preventative Maintenance Monthly
ISSUE 628
MARCH 2005
U
nnecessary tire wear on M939-series 5-tonners in the “sandbox” has more than a
few mechanics scratching their heads.
They’ve checked the CTIS and tire pressure, and it’s on the money. The front
wheels disengage when the Front Wheel Drive Selector lever is moved to the OUT
position.
And even after taking the truck in for a front end alignment, excessive tire wear is
still a problem. What gives?
It could be the truck’s Carden-style CV
joints are worn. They can cause prema-
ture tire wear, especially on older trucks.
To prevent that tire wear, you mechan-
ics can put in more durable CV joints on
both front drive shafts. NSN 2520-00-
734-6985 gets the left side CV joint.
NSN 2520-00-734-6984 gets the right
side joint. The replacement CV joint is
rubber-encased.
Axle Seals
There are two different seal assemblies for the M939A2-series truck’s front axle.
Which seal is used depends on the CV joint.
The shaft diameter on the CV joints is different. That’s why different seals are
found on the same model trucks.
By the way, you don’t need the thrust washer, item 9 shown on Page 3-426 of TM
9-2320-272-24-1 with the new CV joint.
•
Seal assembly, NSN 4320-00-734-6951,
is
used on M939A2-series trucks with the newer
rubber-encased CV joint. This same seal is also
used on M939 and M939A1 trucks.
•
Seal assembly, NSN 5330-01-271-9490,
is
used on
all
M939-series trucks with the original
Carden-style CV joints.
•
Seal, NSN 5330-01-271-9362,
is used on
M939A2-series trucks with the original Carden-
style CV joint.
•
Use the NSNs shown in Fig 236 of TM 9-2320-
272-24P-1 for all other M939-series trucks.
M939/A1/A2-Series Trucks…
PS 628
MAR 05
15
Fuel Tankers…
pack up,
old man!
I’m your
replace-
ment!!
my spring
let me
down.
T
he old-style ground wire clamps used on fuel tankers are known to fall apart
from rust and broken springs.
If you have an old clamp that’s seen its last days, replace it with a more durable
clamp that comes with NSN 5999-00-134-5844.
The new clamp is a snap to install. Remove the old clamp, snip off the wire eye-
let if there is one, and fit the wire into the new clamp. Use a 3/32-in hex wrench
from the No. 1 or No. 2 Common shop set to tighten the clamp’s handle screws to
ground wire.
move
over,
carden.
I’m the
new
cv
joint in
town!
…what
is
causing all this
tire wear?
Here’s the
lowdown
you need to
remember
until this info
is added to
the Tms…
Use Replacement Clamp
I’ve checked
everything on
this truck…
628.14-15(C)
1/25/05
11:37 AM
Page 1
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