Transport (free-wheel) system operation, Theory of operation – John Deere stx38 User Manual

Page 247

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3/21/97

6 - 15

HYDROSTATIC POWER TRAIN

THEORY OF OPERATION

TRANSPORT (FREE-WHEEL)
SYSTEM OPERATION

Function:

The transport (free-wheel) system allows the operator
to push the tractor while the engine is off, transmission
in or out of either forward or reverse, and the brake
released.

Major Components:

• Internal center block relief valve assembly
• Internal actuating assembly
• External over-center actuating lever assembly

Theory of Operation:

K–50 Version Shown

A pair of bypass relief valves (A), located inside the
center block of the transaxle, allow for oil to flow freely
without the pump being turned by the engine and
traction drive system.

When the actuating lever (I) is moved into its over-
center locked position (H), the single chain link
assembly (G) pushes the actuating pin (F) and bracket
(E) against both valve pins (D). As the pins move inside
their guides (B), the return springs (C) become
compressed and the check balls of the relief valves (A)
are unseated; allowing oil to flow freely. This allows the
operator to push the tractor with the engine off and the
brake released.

When the actuating lever (I) is returned to its
disengaged position, the return springs (C) force the
valve pins (D) out, allowing the check balls to seat in
the relief valves (A), stopping oil free flow and the
wheels from turning freely.

M58211

A

M58212

D

C

B

M55843

E

F

M58266

G

H

I

F

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