Hydrostatic transmission trouble shooting – Bolens 138-784-401 User Manual
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HYDROSTATIC TRANSMISSION TROUBLE SHOOTING
No output torque (power) in either
direction, cold start.
1. Reclieck relief valve position, control linkage, input drive.
2. Oil l ivel in reservoir low.
3. Broken control shaft dowel pin. Transmission must be repaired
or replaced.
Loss of output torque, continuous
load.
1.
Opeiating at conditions approaching hydraulic stall. The
trani mission fluid has exceeded 180° F.
2. Intenal leakage due to wear. Transmission should be repaired
or replaced.
3. Watt f in transmission fluid. Purge system of all fluid and replace
with new transmisison fluid. Replacement of the transmission
is ge nerally not necessary.
No output torque in one direction.
1. One of the directional valves is stuck. Transmission should be
repa red or replaced.
2. Low oil level.
Riding mower cannot be pushed
with engine off.
1. Relief valve control not set.
2. Relief valve travel not adjusted.
3. Motor piston or rotor seized. Transmission must be repaired or
replaced.
No neutral.
Recfeck linkage. Loose linkage creates an adjustment problem.
Note The hydraulic neutral band is very narrow. Deflection in
the linkage may make it difficult to obtain neutral from both direc
tions It is recommended that neutral should be positive from
forwcTd drive.
Oil leakage at the control shaft seal.
1. Spillage when fluid has been added to the reservoir.
2. Spillage at the vent in the reservoir at operating temperatures
due 1o cold level being too high or water in the fluid. Reduce
fluid evel or replace fluid in the event there is water in it (milky
color.
3. Loosn oil reservoir or cover.
4. Loos 5 vent bolt.
5. Damaged control shaft seal. Transmission should be repaired.
Noisy operation.
1. Oper iting at part throttle. Hydrostatic transmission is designed
to operate with the engine running at full throttle.
2. Water in transmission fluid. Replace transmission fluid.
3. Air in transmission fluid. Bleed air from vent.
Output shaft rotates in the opposite
direction.
The transmission body is 180° out of position. Transmission
has t3 be removed and reassembled correctly.
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