Lull 1044C-54 Series II Service Manual - Manual (Page 326)

Transmission
8-2 31200079
The ZF 4 WG-98 TC Transmission used in this vehicle is a four-speed
configuration. The “intermediate drop” designation refers to the relative top-to-bottom
length of the transmission case, chosen for its compatibility with vehicle chassis
and operating requirements. Intermediate drop does not refer to an operational rpm
shift or drop.
Transmission Operation
The transmission is mounted to the frame by front and rear mounting brackets and
rubber isolator pads. Power from the engine is transmitted to the transmission by
means of a drive shaft, bolted to the engine flywheel and a torque converter at the
transmission input. The transmission in turn transmits power to the drive shafts,
driving the front and rear axles.
The torque converter consists of three main components: the impeller (driver),
stator and turbine (driven) in an oil-filled, enclosed housing. As the torque converter
is driven by the engine flywheel, the impeller (pump) wheel rotates, forcing oil
through the stator, which is held stationary by the stator shaft bolted to the
transmission housing. This directs the moving oil onto the vanes of the turbine
(driven) wheel, causing the turbine wheel to rotate. The turbine wheel is connected
to the transmission input shaft, and transfers power to the transmission. Oil from
the turbine wheel is then returned to the impeller wheel to repeat the process. This
process results in an increase in the torque available at the transmission input
shaft.
The transmission and torque converter are powered by their own internal hydraulic
(“transmission fluid”) system, separate from the vehicle hydraulic system.
Pressurized oil for the valve control circuits and torque converter is supplied by a
pump located at the rear of the transmission. The pump is driven by the central shaft,
which in turn is connected to the impeller of the torque converter. The vehicle is
equipped with an external oil cooler to cool the transmission oil.
The transmission gear (“speed”) select lever, an electric shift control, is located on
the left side of the steering column in the operator’s cab. Movement of the gear
select lever energizes the selected transmission shift solenoid valves, which, in
turn, direct the transmission fluid under pressure to the selected forward or reverse
valve and to the designated range (gear or “speed”) clutch. Several factors,
including terrain, loading, engine rpm, axle/wheel-end gearing and the selected
transmission gear, determine actual vehicle speed.
To engage the clutch, the gear select lever is placed in the desired direction
(forward or reverse) and range (gear or “speed”) position. The gear select lever
movement energizes the selected direction and range (gear) solenoids, allowing
transmission fluid under pressure to flow through tubes and passages to the
selected clutch shafts. Oil sealing rings are located on the clutch shaft; these rings
direct oil under pressure through a drilled passageway in the shaft to a desired
clutch. Hydraulic pressure forces the piston and discs against the back-up plate.
Discs, with edge tangs, clamp against toothed discs on the inner diameter,
enabling the hub and the clutch shaft to lock together and drive as a unit,
providing output power.
Transmission Serial Number
The transmission serial number plate (1) is located on the pump side (front) of
the transmission at the bottom right, toward the vehicle frame. Information
specified on the serial number plate includes the transmission model number,
the transmission serial number and other data. Information on the serial
number plate is required in correspondence regarding the transmission.