John Deere stx38 - Manual (Page 242)

6 - 10
3/21/97
THEORY OF OPERATION HYDROSTATIC POWER TRAIN
THEORY OF OPERATION
In this group the STX hydrostatic power train is
separated into the following systems:
• Belt Traction Drive System
• Transaxle and Shift Linkage System
• Brake/Neutral Return System
• Transport (Free-Wheeling) System
BELT TRACTION DRIVE SYSTEM
OPERATION
Function:
The function of this system is to transfer power from
the engine to the hydrostatic transaxle.
Major Components:
• Foot pedal and brake linkage
• Engine drive sheave
• Traction drive belt
• Tensioning idler assembly
• Tensioning spring
• Adjusting idler assembly
• Transaxle drive sheave
Theory of Operation:
As soon as the engine is cranking, the engine drive
sheave (A) pulls the drive belt (D). The drive belt,
having been tensioned by the tension spring (B) and
idlers (C and H), transmits power to the transaxle drive
sheave (E). With the brake pedal linkage (I) released
and hydro control linkage (F) engaged, the hydrostatic
pump and differential matrix (G) drives the unit.
TRANSAXLE AND SHIFT LINKAGE
SYSTEM OPERATION
Function:
The transaxle transmits power from the engine,
through the belt traction drive system, through the
transaxle’s hydraulic pump and motor center block
matrix into the differential assembly and out the drive
axles to the rear wheels. The transaxle provides infinite
ground speed selections up to 5 mph in forward and up
to 2.6 mph in reverse.
It also provides the means to interrupt the flow of power
when shifted into neutral.
Major Components:
• Transaxle drive sheave and fan
• Pump (input) shaft and cylinder block assembly
• Shift linkage and pump swashplate assembly
• Center block assembly
• Motor cylinder block assembly and drive shaft
• Differential assembly and axle shafts
• Wheels and tires.
Theory of Operation:
Neutral:
As soon as the engine is running, the traction drive belt
(A) turns the transaxle input sheave and fan (B) rapidly
in a clockwise direction. The sheave hub is splined and
retained by a flat washer and flanged cap screw onto
the splined pump (input) shaft (C).
A
C
D
E
M58258
I
H
G
F
B
M58253
A
B
C