LR3/Disco 3
There are three drive clutches and two brake clutches used in the 6HP26 transmission. Each clutch comprises one or
more friction plates dependent on the output controlled. A typical clutch consists of a number of steel outer plates and
inner plates with friction material bonded to each face.
The clutch plates are held apart mechanically by a diaphragm spring and hydraulically by dynamic pressure. The pressure
is derived from a lubrication channel which supplies fluid to the bearings etc. The fluid is passed via a drilling in the output
shaft into the chamber between the baffle plate and the piston. To prevent inadvertent clutch application due to pressure
build up produced by centrifugal force, the fluid in the dynamic pressure equalisation chamber overcomes any pressure in
the piston chamber and holds the piston off the clutch plate assembly.
When clutch application is required, main pressure from the fluid pump is applied to the piston chamber from the supply
port. This main pressure overcomes the low pressure fluid present in the dynamic pressure equalisation chamber. The
piston moves, against the pressure applied by the diaphragm spring, and compresses the clutch plate assembly. When
the main pressure falls, the diaphragm spring pushes the piston away from the clutch plate assembly, disengaging the
clutch.
PLANETARY GEAR TRAINS
The planetary gear trains used on the 6HP26 transmission comprise a single web planetary gear train and a double web
planetary gear train. These gear trains are known as Lepelletier type gear trains and together produce the six forward
gears and the one reverse gear.
Single Web Planetary Gear Train
The single web planetary gear train comprises:
Item Part Number
Description
1
-
Input shaft
2
-
Main pressure supply port
3
-
Piston
4
-
Cylinder – External plate carrier
5
-
Clutch plate assembly
6
-
Baffle plate
7
-
Diaphragm spring
8
-
Output shaft
9
-
Bearing
10
-
Dynamic pressure equalisation chamber
11
-
Piston chamber
12
-
Lubrication channel
