JLG TF6-42 Service Manual - Manuale (Pagina 729)

T12000 ID 04/99 7-1
7. TROUBLESHOOTING GUIDE FOR THE T12000 TRANSMISSION
The following information is presented as an aid to isolating and determining the specific problem area in a
transmission that is not functioning correctly.
When troubleshooting a “transmission” problem, it should be kept in mind that the transmission is only the
central unit of a group of related powertrain components. Proper operation of the transmission depends on
the condition and correct functioning of the other components of the group. Therefore, to properly diagnose
a suspected problem in the transmission, it is necessary to consider the transmission fluid, charging pump,
torque converter, transmission assembly, oil cooler, filter, connecting lines, and controls, including the engine,
as a complete system.
By analysing the principles of operation together with the information in this section, it should be possible to
identify and correct any malfunction which may occur in the system.
7.1 T12000 TRANSMISSION
T12000 (power shift with torque converter transmission) troubles fall into three general categories:
1. Mechanical problems.
2. Hydraulic problems.
3. Electrical problems.
In addition to the mechanical and electrical components, all of which must be in the proper condition and
functioning correctly, the correct functioning of the hydraulic circuit is most important. Transmission fluid is
the “life blood” of the transmission. It must be supplied in an adequate quantity and delivered to the system
at the correct pressures to ensure converter operation, to engage and hold the clutches from slipping, and to
cool and lubricate the working components.
7.2 TROUBLESHOOTING PROCEDURES
7.2.1 Stall Test
A stall test to identifies transmission, converter, or engine problems.
Use following procedure:
1. Put the vehicle against a solid barrier, such as a wall, and/or apply the parking brake and block the
wheels.
2. Put the directional control lever in FORWARD (or REVERSE, as applicable).
3. Select the highest speed.
With the engine running, slowly increase engine speed to approximately one-half throttle and hold until
transmission (converter outlet) oil temperature reaches the operating range.
CAUTION
D
O NOT OPERATE THE CONVERTER AT STALL CONDITION LONGER THAN
30
SECONDS AT ONE TIME
,
SHIFT TO NEUTRAL
FOR
15
SECONDS AND REPEAT THE PROCEDURE UNTIL DESIRED TEMPERATURE IS REACHED
.
E
XCESSIVE TEMPERATURE
120 °C (250 F)
MAXIMUM WILL CAUSE DAMAGE TO TRANSMISSION CLUTCHES
,
FLUID
,
CONVERTER , AND SEALS .