MASSEY FERGUSON 5400 - General

Massey Ferguson 5400 - Issue 1.a
06E01.3
GPA20 differential
A . General
The bevel gear rotation is provided by the output shaft
of the gearbox and drives the rear axle. The helical
drive pinion is supported on either side of its teeth by
two taper roller bearings fitted in opposition. Lubrica-
tion of the bearing (30)(37) is ensured by a flow of
transmission oil from the PTO upper cover located at
the rear of the tractor (see section 7). The bearing
cones are force fitted to the drive pinion and the rear
cup, smeared with Loctite 603, is also force fitted in
the rear axle housing. The front cup is free in its bore
to allow for shimming of the drive pinion.
The ring gear is fixed to the differential unit by rivets.
The differential assembly turns on two taper roller
bearings supported by two lateral flanges centred by
rings and screwed to the rear axle housing.
The differential assembly comprises two half-housings
holding two pinion gears for models up to 75 hp and 4
pinion gears for models whose power exceeds 75 hp.
The housing also holds two sun gears. The drive pinion
is fitted in the rear axle housing.
The bevel gear is adjusted using shims fitted between
the centre housing and the bearing cup (37).
The pre-loading of the taper roller bearings (31) (33)
and (30) (37) is obtained by shim(s) placed between the
handbrake plate and the centre housing.
The pre-load shimming of the differential assembly is
carried out by deflectors (13) of different thicknesses
placed behind the left-hand bearing cup (14). If needed,
an additional shim (49) can be fitted between flange (9)
and the deflector.
Differential lock
The left-hand flange contains the differential lock
mechanism. The system consists of a piston and a
mobile coupler integral via splines with the input sun
gear in the left-hand trumpet housing. The mobile
coupler is moved by the piston which is supplied by
the 17 bar hydraulic circuit via a solenoid valve fitted on
the right-hand cover. The piston moves and pushes
against the mobile coupler, compressing the spring.
The teeth of the mobile coupler engage with a fixed
coupler that is integral with the differential unit. In this
position, the input sun gears of the left- and right-hand
side trumpet housings turn at the same speed. When
the pressure is released, the mobile coupler is forced
backwards by the spring.