Dismantling and Reassembly of the Vauxhall Cavalier 4 x 4 Transfer Box

A. It is assumed the reader has removed the txb and/or read the removal section.
B. There are no parts in the txb which can be replaced off the shelf.
C. Any assemblies requiring replacement will usually be best served by obtaining second hand parts. SUMMARY
1. Split the box into three component parts.
2. Test the pressure plate and seal.
3. Dismantle and inspect the clutch plate assembly.
4. Reassemble the txb.
5. Difference's between pre & post 1992 txb's.
Description - The transfer box (txb) consists of a crown wheel and pinions, a 'motor cycle' multi-plate type clutch, a pressure plate assembly (or ram) and a viscous coupling. The txb is driven by a splined coupling from the gearbox and the offside drive shaft is coupled to the gearbox by an extension shaft running inside the splined coupling. (i.e. through the txb)
The txb clutch provides the connection between the front and rear wheels. It is engaged when fluid pressure from the power steering pump circuit is applied to the pressure plate actuator ring (Fig.2A & 7). The clutch (and 4WD) is engaged when the engine is started and all the time except at above 16 mph when the brakes are applied. Drive is applied to the rear wheels by the txb clutch and through the viscous coupling, which provides the power split. It is the heavy component (Fig.2B) at the rear of the txb, which connects to the propshaft. An electrical solenoid, situated on the accumulator block, switches the pressure necessary to operate the pressure plate assembly (or ram). Fluid pressure applied to the txb is monitored by a pressure switch, which operates when sufficient pressure is applied to the txb. The accumulator (round bulb on the NS bulkhead) is the place where fluid can accumulate while all this is going on. It is why you have to apply the foot brake 25 times before checking the 'steering pump oil level' - to empty fluid back to the reservoir. The reason why it is essential to keep the tyres within 2mm tread wear of each other and only change tyres as a set, is that when the 4WD is engaged, the difference between the running speed of the front and rear wheel sets, with uneven tyres, would cause the viscous coupling to overheat and damage the box. - Called 'Transmission Wind Up'.

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