309-00A Exhaust System 4.0L: Description And Operation (page 2 of 3)

GENERAL 

The 4.0L V6 exhaust system is fabricated from stainless steel and is supplied as three separate assemblies; a LH front 
section incorporating a catalytic converter, a RH front section incorporating a catalytic converter and a rear section 
incorporating a front silencer (non-NAS only), a centre silencer and two rear silencers. 
 
The system is attached to the underside of the body with five mounting rubbers which are located on mild steel hanger 
bars that are welded to the system. The mounting rubbers locate on corresponding hangers which are welded to the 
underside of the vehicle body. The system is routed mainly on the inside of the LH chassis longitudinal before splitting 
near the rear differential to exit at each side of the rear of the vehicle. 
 
The system has service repair items available. Indentations in the rear section, between the center and the rear silencers, 
show the cut points for the service replacement rear silencers or front section. When a service repair section is used, the 
joint is connected using a sleeve and two clamps to connect the pipes at the cut points. 
 

FRONT SECTION 

Both front sections have a welded flange with two holes which provide for the attachment with two bolts to the LH and RH 
exhaust manifolds. The flange is sealed by a tapered seat in the flange and a machined cone on the manifold. 
 
The flange is welded to a short, straight pipe, which in turn is welded to the body of the catalytic converter. The pipe has a 
threaded boss which is welded over a hole in the pipe to provide location for the pre catalyst heated oxygen sensor 
(HO2S). 
 
On the LH front section, the converter outlet pipe is a 55 mm (2.16 in) diameter tube, with a 1.5 mm (0.06 in) wall 
thickness, which is welded to the converter body. The rear of the outlet pipe is inserted into the flared end of the rear 
section. A clamp is used to compress and secure the joint. 
 
On the RH front section, the converter outlet pipe is a 55 mm (2.16 in) diameter tube, with a 1.5 mm (0.06 in) wall 
thickness, which is welded to the converter body. The rear of the pipe curves left, under the transmission and then curves 
again to run parallel to the LH pipe. The end of the pipe has a welded flange with two holes which locate on two studs on 
the rear section and is secured with nuts. A metal gasket is used to seal the joint between the front and rear section 
flanges. 
 
Both the LH and RH converter outlet pipes have a threaded boss which is welded over a hole in the pipe to provide 
location for the post catalyst HO2S. 
 

REAR SECTION 

The rear section has a short 55 mm (2.16 in) diameter tube, with a 1.5 mm (0.06 in) wall thickness, which is flared to an 
inside diameter of 55 mm (2.16 in) to locate the LH front section. The tube is welded to the front silencer assembly. A 
second short 55 mm (2.16 in) diameter tube, with a 1.5 mm (0.06 in) wall thickness, has a welded flange with captive 
studs to provide attachment for the flange on the RH front section. This tube is also welded to the front silencer assembly.
 
The front silencer comprises a single skin and two end plates which are welded together which give a capacity of 6.4 litres 
(390.5 in

3

). The silencer contains baffles and perforated tubes which reduce noise as the exhaust gases pass through the 

silencer. A hanger bar is welded to the front of the silencer and provides for the location of a mounting rubber. 
 
The silencer has two short 55 mm (2.16 in) diameter outlet pipes, with a 1.5 mm (0.06 in) wall thickness, which connect to 
the centre silencer. 
 
The centre silencer comprises two pressed stainless steel shells which are welded together to give a capacity of 25.2 
litres (1538 in

3

). The silencer contains baffles and perforated tubes which reduce noise as the exhaust gasses pass 

through the silencer. A hanger bar is welded to the front right hand side of the silencer and provides location for a 
mounting rubber. 
 
The silencer has two 55 mm (2.16 in) diameter outlet pipes, with a 1.5 mm (0.06 in) wall thickness, which are curved to 
pass around the rear suspension components. 
 

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RH manifold

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Mass damper