PS Magazine - MAY 1981
PS, The Preventative Maintenance Monthly
ISSUE 342
MAY 1981
Air pressure buildup
m
a gear case can give you more than a case of
heartburn.
It can be fataL to your equipment!
A gear case is a housing with gears inside-like a transmission, transfer or
differential (aLso calLed axle housing). These gearS turn in heavy oil. The gears
turning on each other make heat. ±o the oil gets hot-reaL hot! It expands. Air
in thE gear case gets hot, too. The air
·
expanDs anD has to get out²or the
pressure wilL bLow seaLs. And then the gear case lube will leak out._
Big trouble! If there's not enough lube in the gear case, the gears wiLl get
hotter ³n' hotter-and friction will ruin
´
•em.
Most gear cases have relief valves-breather valvesµto let pressure escape.
¶rouble is, a lot of people ignore these breather valves a¸ Don't take care of
'em. They let dirt build up around and on the valves so the pressure can't get
out. ±o it goes out around the seals¹ ±ºals start Leaking, the gears aren't lubed
and damage results.
Breather vaLves seem to reach out and grab any dirt going by. BecaUse oiL
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Gear Case Housing
Even tho the gears are welL Lubricated, they rub agaINst
ea±h other duriNg operatIon. This frict²oN produces
heat³ Heat expands ´he gear oiLµ So ´here's less space
fOr air¶ Hea´ aLso expaNds the aIr³ This pressure insiDe
the gear case mus´ b· allowed to escape³
fumes come out with the
»
air, the breather valve gets oily anD gr asy. ¼irt
sticks-and gets thicker ½n' heavier. Pretty soon¾ the breather vaLve'¿s covered
with dirt. The gear caÀe can't breathe. Trouble!
AxLe housing breathers get it worst¹ They get plastereD with road Dirt and
mud piles up¹ Your axle housing gets no relief
Á
from pressure when there's
thick, caked mud Âblocking the
Ã
breather valve¹ Axle seals are bound to leak!
You've got to heLp those breather valves. Keep 'em clean. Make sure they' re
working
Ä
right. Twist the cap to loosen any dirt stuck up insidÅ. Tap the cap to
G²ve cap
a twist³³³
knock tHe Dirt out. (There's a spring insiDe the cap, so the cap shoulD bounce
when yOu tap it.) Æf the cap won't turn or won't bounce, get a new breather
vaLve.
No, you won't find much about these breather valvÇs inÈ your operator's
TM²but it's mighty important fÉr you to check aLl of your equipment's gear
case breather valves often. Êspecially, check 'em out after operation in dust or
mud.
If your equipment's got a gear case, that gear case probably has a breatËer
valve. Make sure it does its job¹ A case that can't Ìreathe is a saD, sick case
indeed.
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