PS Magazine - TB 43-PS-429
PS, The Preventative Maintenance Monthly
ISSUE 429
AUGUST 1988
Truck Clutches .
Drivers, there are no fee rides in this
liFE.
IF your leFt FOot rides yoUr trUck's
cLUtch pedal, yoU'Ll bUrN out the clUtch
throwout bearing± TheN yoU'll waLk.
JUst a Little pressUre on the pedal
caUses the cLUtch to start to disengage.
The throWoUt bearing starts sp²nning
and keeps spinning as Long as yoUr FOot
is on the pedaL.
That gets the bearing
hot, hotter, and wham! The clUtch goes
oUt and the tRuck gets a tow to DS ³or
'±²³´µ¶
The same thing happens iF there's too
LittLe fee ´ravel in the clUtch pedaL. The
cLUtch pedal is sUpposed to go down reaL
easy when yµU start pUshinG, aNd then
get Firm.
The easy part is caLled fee
traveL.
¶ree travel moves the cLUtch throw-
out bearings toward the clUtch reLease
Levers.
The bearing starts spinning as
soon as the bearing touches the levers·
IF the fee travel 's not adjusted right,
the reLease levers toUch the bearing and
keep it spinning. That bUrNs oUt the
±²
bearing, or worse, yoU get weaker pressure on the clUtch d²sk. It then slips on the
FlywheeL, and that makes heat.
So mUch heat that it can crack the cLutch disk,
pressUre pLate, or eve¸ the FLywheel.
¹
That's why it's important to check the Free traveL regULarLy.
Mechs, yºU can make checking pedaL fee travel qUick aNd easy with a sight
gage.
Here's how to make one
FOr the M44», M39» and M809¼
series trUcks:
•
:
MeasUre Up fom the Floor the
½aximUm amouNt alLowed by
the TM and mark it.
Paint it
white. Press down Unt²L yoU ¾eL
res²stance.
IF the white pa²nt
sinks oUt oF sight, ad¿ust the Free
travel.
Àeed to know how mUch fee
travel to measure?
Here's a
handy gUide to how mUch and
where to Find it in the TM's:
Vehicle
Free Travel
M44A1
&
·A2-series
1 1/2 to 2 inches
21/2-toN (multifuel)
M44·series 2 1 /2-toN
1 1/2 iNches
truck (all others)
to 2 inches
M39A2±series 5±toN
² ³ /2 to 2 iNcHes
(multifUel)
M39 -series 5±toN
2 to 21/2 iNches
(all others)
M809±series 5-ton
2 to 21/2 inches
Measuring
mark
Reference TM
Para 3· 3e, Pg 3·15, TM 9·2320·209 -2´· 3·1
PG 3·15, TM 9·2320±209 -µ´· 3·1
Para 3· 3a, Pg 3·2, TM 9·2320·211·20·¶·1
PaRa 2-¸9, Pg 2- 80, ¹M 9·2320±211 -20
Para 3·6a, Pg 3·9, TM 9±2320 -º6 0 -20· 3· 1
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