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Vehicle
Information: 1994
Jeep Wrangler, manual transmission, 4WD, 4.0L I6 cylinder, 85,000
miles.
These are basic information on how my husband and I installed
a 1997 Jeep Wrangler 4.0L exhaust collector pipe on our 94 Wrangler.
Use this information AT YOUR OWN RISK!
PLEASE NOTE : This write-up is for REFERENCE ONLY. The parts
you buy and the vehicle you own will ultimately determine exactly
how you complete this modification. Not all Wranglers are the
same year to year - and you may discover your vehicle can and
might be different than mine.
Why
change the stock exhaust??:
On the older Jeep Wranglers (95 and older - YJ's) the exhaust
is routed underneath the transmission and is vulnerable while
offroading. I have an engine skid plate under my Jeep - which
has protected the exhaust and engine for atleast 4 years, however....
the clearance inbetween the exhaust and the engine skid was
about 1/4" or less. During certain offroad situations -
I'd land on the engine skid causing it to bend upward causing
the exhaust to rest directly on the engine skid plate. For many
years - I'd remove the engine skid plate and have it straightened
(park a vehicle on it) and put it back on again (gain about
1/8" clearance between the engine skid and exhaust). I
got tired of removing the engine skid after each trip. Putting
the TJ exhaust on will eliminate this problem because the exhaust
routes in front of the oil pan and never crosses underneath
the transmission.
Without
Engine Skid plate - stock YJ exhaust
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With
Engine Skid Plate - stock YJ exhaust
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Parts
Research: I
spent some time researching my optoins of ordering parts - calling
Auto Stores and junkyards. The Auto stores told me, "That's
a dealer only item - I can't get them here" and the junkyards
aren't allowed to sell used catalytic converters and were againest
cutting it off and selling the part without it. I could've tried
harder and searched more - but I decided to call up a good friend
of mine who works at the dealership. He hooked me up with a
new 97 Jeep Wrangler 4.0L collector pipe - including a new catalytic
converter (attached as one unit) & hardware for a very good
price. Thanks Scott!!!
Below is a picture of the stock 97 TJ 4.0L collector
pipe with catalytic converter (LEFT)
And the stock 94 YJ 4.0L collector pipe with catalytic converter
(RIGHT)
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Removal
of stock YJ Collector pipe
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Remove
the stock YJ collector pipe & catalytic converter
up to the muffler. Keep the Muffler intact and hanging
in place. You will attach the TJ pipe to the original
YJ muffler.
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Test
Fitting
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The
new collector pipe came with a header gasket and new bolts.
We tried to remove the old bolts from the YJ header with
no results and we didn't want to damage anything on the
header. We kept the old bolts intact and installed the new
gasket. Put the new collector pipe on and hand tightened
it in place. We kept it loose fitting for now while looking
for any issues and parts that we'll need to make this work.
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Transmission
mounted exhaust hanger
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The
hanger on both TJ pipe and YJ pipe are in the same place
- which is good. However, you'll need to remove the
inner rubber teardrop shaped bushing that's inside the
bracket on the transmission. The original teardrop bushing
had a "U" shaped hole in the bushing. You'll
need a round hole inside this bushing. I was able to
find a teardrop bushing (w/ round hole) from the spare
parts I have in my basement - however, the hole wasn't
big enough.
If
you go to a junkyard - most YJ rear hangers are equipped
with the teardrop bushing with a round hole that'll
need to be made larger. You'll want to drill or ream
the hole out much bigger (1/2" or so) due to the
rubber expanding. When you're done drilling/reaming
- the rubber will contract smaller and should match
closely to 9/16" hole that you need.
(LEFT)
- picture of the teardrop bushing with the 9/16"
hole.
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Oxygen
Sensor wiring
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The
oxygen sensor wiring on the YJ is too short to reach the
bung on the TJ collector pipe. After some research - we
found that lengthening the wiring would not cause any negative
effects on the O2 sensors feedback to the computer. My husband
spliced in the wiring to make it long enough.
Note: The 97 collector pipe has a secondary O2 sensor bung
after the catalytic converter that will need to be plugged.
(TOP Sensor - below picture) Lengthened
(BOTTOM Sensor - below picture) Original length O2
sensor |
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TJ
Collector Pipe too short to reach Muffler & Second
O2 sensor bung
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While
the collector pipe was still in place during our TEST
fit - we discovered the pipe was just a bit too short
and didn't reach the muffler. I went to a local exhaust
shop and requested a piece of pipe 6" long with 2.25"
inner diameter on the pipe end and 2.5" inner diameter
on the muffler end.
After
installing this extenstion piece, we were able to tighten
down the exhaust at the header and get a clearer idea
of how things look.
(BELOW) - You can clearly see the extension piece
we've added to mate up to the muffler. On the left of
the extention piece, you can see the second O2 sensor
bung. I had a spare O2 sensor that I used to plug the
hole temporarily until I find the proper sized pipe plug
to fit.
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Clearance
Issues
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After
installing the extension piece - we noticed the entire
exhaust was sitting about 2" lower than the original
set-up. The new catalytic converter is more rounded and
larger than the original. It was resting directly on the
transfercase crossmember. Not good....
To
remedy this - we went back to the exhaust shop and had
them bend a custom piece of pipe with a 2" elevation
(2.25" inner diameter on both ends). The piece ended
up being approximately 18" in length total. We had
to cut about 12" out of the TJ collector pipe to
fit this elevation pipe in. Installed this just prior
to the transfercase cross member.
(TOP
Picture below) - the elevation pipe installed.
(Bottom Picture below) - Clearance after the elevation
pipe was installed. Take notice to the finalized exhaust
hanger in the right of the picture.
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Final
Inspection & Completion
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After
the elevation pipe was installed - we tightened everything
down enough for a test with the motor running. We cranked
the engine over and everything was fine!!
FINAL
Pictures
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Picture
from front -
without engine Skidplate
(immediately after installation)
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Picture
of oil pan -
without engine Skidplate
(immediately after installation) |
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Picture
of the transmission - with engine Skidplate
(picture taken after some
road & trail miles) |
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Picture
of the front -
with engine Skidplate
(picture taken after some
road & trail miles) |
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Picture
of the side -
with engine Skidplate
(picture taken after some
road & trail miles) |
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