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17 - 2
SPRINGS/SHOCK ABSORBERS
•
Fig. 3 Progressive-Type
Rear Leaf Spring
A progressive-rate type leaf spring has two stages.
The first stage, comprised of the upper leaves, pro-
vides a l o w spring rate w i t h a l i g h t cargo load. The
lower leaves (second stage) g r a d u a l l y interact w i t h
the upper leaves a n d provide a n increased s p r i n g
rate for medium-to-heavy cargo loads. T h i s t y p e o f
s p r i n g ( p r o g r e s s i v e ) i s n o t t h e s a m e as a
fixed-
r a t e w i t h a u x i l i a r y s p r i n g t y p e o f t w o - s t a g e l e a f
s p r i n g ( w i t h t h e a u x i l i a r y s p r i n g l o c a t e d a b o v e
t h e m a i n leaf).
VEHICLE CONFIGURATION
The f r o n t "eye" o f each leaf spring is attached t o a
bracket t h a t is r i v e t e d to t h e frame side r a i l . The
rear "eye" o f each standard equipment leaf s p r i n g is
attached t o the frame side r a i l v i a a one-piece spring
shackle w i t h a one-piece, "pressed-in" rubber bush-
ing.
The rear leaf springs are attached to the axle shaft
tubes a t t h e s p r i n g pads b y U-bolts and nuts.
SHOCK ABSORBER DESCRIPTION
Dual-action, gas-charged, h y d r a u l i c shock absorb-
ers are used w i t h b o t h the front and rear suspension
systems for R a m T r u c k and Ramcharger
vehicles.
The shock absorbers are designed to dampen t h e ve-
hicle body (i.e., spring) "up-down" movement. I n ad-
dition, rubber bushings are inserted i n t o the shock
absorber "eyes" to dampen o u t road/street surface
"shock" a n d noise.
The f r o n t a n d rear springs allow t h e wheels to
move u p and down w i t h the road/street surface semi-
independent o f t h e vehicle chassis a n d body. How-
ever, t h e springs alone cannot provide a completely
smooth r i d e because of the energy t h a t is stored i n
t h e springs d u r i n g compression a n d t h e n released
d u r i n g rebound. I f a s p r i n g is unrestrained, t h e en-
ergy w i l l be alternately stored and released and t h e
s p r i n g w i l l continue to oscillate i n t h i s manner u n t i l
t h e vehicle w e i g h t dampens t h e oscillations (move-
ments). A shock absorber is designed t o i m m e d i a t e l y
dampen t h e s p r i n g movements b y dissipating most o f
t h e s p r i n g energy, w h i c h w o u l d otherwise continue t o
be a l t e r n a t e l y stored and t h e n released.
A shock absorber converts mechanical s p r i n g en-
ergy i n t o heat energy v i a t h e f r i c t i o n caused b y t h e
h y d r a u l i c f l u i d ( i n t h e shock absorber) w h e n i t is
forced t h r o u g h restricted passages. T h i s causes t h e
s p r i n g to r e t u r n smoothly t o i t s n o r m a l position (i.e.,
t h e s p r i n g movement is dampened).
VEHICLE
CONFIGURATION
For 2 W D vehicles, a front shock absorber is located
inside each f r o n t spring coil. I t i s attached to t h e
frame side r a i l bracket and t o t h e lower suspension
a r m (Fig. 1).
For 4 W D vehicles, t h e f r o n t shock absorber upper
ends are attached to brackets located on t h e frame
side r a i l . T h e lower ends are attached to t h e f r o n t
axle shaft t u b e brackets.
The rear shock absorber upper ends are attached t o
t h e frame crossmember a f t of t h e rear axle. T h e
lower ends are attached t o t h e spring brackets (at
t h e axle shaft tubes).
R a m
T r u c k a n d Ramcharger
vehicles
are also
equipped w i t h jounce bumpers located a t the f r o n t o f
t h e vehicle. T h e bumpers are attached t o t h e shock
absorber brackets in-line w i t h t h e axle shaft tubes.
VEHICLE LOADING AND WEIGHT DISTRIBUTION
A R a m T r u c k or Ramcharger vehicle should always
be loaded so t h a t t h e vehicle weight c e n t e r - l i n e i s
located i m m e d i a t e l y forward of the rear axle. Correct
vehicle l o a d i n g provides proper " f r o n t tire-to-road"
contact a n d t h i s results i n m a x i m u m vehicle h a n -
d l i n g s t a b i l i t y a n d safety. Incorrect vehicle w e i g h t
d i s t r i b u t i o n can cause excessive t i r e tread
wear,
s p r i n g fatigue or failure, and/or erratic steering ( w i t h
extremely incorrect weight distribution).
I n c o r r e c t v e h i c l e w e i g h t d i s t r i b u t i o n s h o u l d b e
c o n s i d e r e d a s a p o s s i b l e cause d u r i n g d i a g n o s i s
f o r e r r a t i c s t e e r i n g , s p r i n g f a i l u r e , and/or exces-
s i v e t i r e t r e a d w e a r c o m p l a i n t s .
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