Tools, Prep and Concerns
I understand that many of you my have concerns about tackling a
transfer case rebuild and possibly even more about having to wire
an electronic controller into your vehicle. Let me start by
saying that I am, at best, a backyard mechanic and that while I do
have some skills, I don't have a fancy shop or too many specialty
tools at my immediate disposal.
I point this out because I truly believe this is an
installation where you can buy the products directly from JB and
in a weekend of time in your garage you can save yourself some
money by "doing it yourself." This installation was done entirely in my two car garage using
basic hand tools and a small set of air tools powered by the
Craftsman compressor my wife and daughter bought me a few years
ago for Father's Day.
In anticipation of doing this project yourself, I can tell that
you will need only a few things that you may not have:
- A chisel
- A pair of flat blade snap ring pliers (it can be done
without these but it makes life much easier)
- A good quality torque wrench - which you
should already have in your tool box for any job you perform on
your 4x4. For this job you will need one that reads all the
way up to 180 ft. lbs.
- A Service Manual for your vehicle.
Installation:
I decided to take JB Conversions' advice and take the 231 out
of the vehicle. I'm not really sure why someone would attempt
this modification with the t-case still in the vehicle since it's easy and quick to remove it.
For the rest of the installation I used their instructions as
a very basic guide to what needed to be done in order, but because
I found their instructions to be adequate but lacking in specific
detail, I referred to the factory service manual for specifics
on what to remove and how best to remove it. I will point
out below areas where you may need a little more help than provided
by JB Conversions.
Note: As I have said in past articles, I am not out to duplicate
the installation instructions from the manufacturer. JB
has a good set of instructions with only one major oversight
that I found. I will not take you thru a complete step-by-step install, but rather will touch on the highlights, leaving
the reader to review the the instructions (available on JB Conversion's
website) and the service manual as they see fit.
The first thing I did was place a jack stand under the back
of the 231 and place a jack under the transfer case skid plate.
Then I unbolted the six bolts that hold the plate to the bottom of
the frame. I then removed the four nuts that hold the skid
plate to the transmission/transfer case mount (this is a great
opportunity to check your transmission mount. As usual, mine was
busted, so I replaced it. For more info on changing a tranny mount, check out this article on
How to Replace the TJ Transmission Mount). After
removing the two bolts that tie my engine skid plate to the t-case
skid plate I lowered the jack and took the transfer case plate out
from under the jeep.
With the t-case plate removed, I placed the jack at a good balance point on the transfer
case and jacked it up until it was lifted off the jack stand.
I shortened the jack stand and moved it to a suitable position forward
of the transfer case. I used the transmission mount.
I then lowered the t-case back down until it was sitting firmly on the
jack stand, but I didn't remove the jack - I left it in place to
provide support for the transfer case. Then I drained the fluid
out of the transfer case.
The next step was to remove the two electrical connections to
the transfer case. The first is at the backside and it is
the speedometer connection (note this for later). The second
is on the drivers side and goes to the 4 wheel drive indicator
on the dash board.
I then removed the six 14 mm nuts that face the transmission.
This is pretty easily accomplished, except for the two upper nuts
on the passenger side. Depending on the size of your
forearms you may find some difficulty getting a good stroke with
your wrench because of the muffler. Be patient and they will
all come out.
After all the nuts were removed, I pulled the shift lever brackets
off the studs and tucked the bracketry up and out of the way so it
didn't catch on anything as I lowered the transfer case.
Slowly rock the transfer case back and forth, watching the studs
to see how far it is moving apart from the transmission. There may be some fluid
loss between the transmission and transfer case when the seal
separates, but it is normal and nothing to worry about.
Once I cleared the studs, I balanced the transfer case on the
jack with my hand and had a helper lower it to the ground and
then simply slid the jack out from under the vehicle. Obviously,
having a friend help you at this point makes the job a lot easier,
but it can be done by one person.
The Teardown:
(Some pics
courtesy of JB Conversions Instructions)
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Transfer case out and on the work bench.
Notice the Currie flange instead of the normal 231 rear
output shaft. |
Standard 231 rear output shaft and housing |
Since I already had a SYE installed on my transfer case, I could
immediately get started, but for those of you following along at home
who have a stock 231, you will need to remove the dust shield and
the rear output seal. Both of these are detailed in the JB
Instructions and shouldn't be too much of an issue. Then remove the main shaft
retaining ring and the spacer which is underneath the ring.
Set them aside because you will not need them again.
I then unbolted the rear bearing housing by removing the five
bolts holding the housing to the back half of the case. Once
the bolts are removed you may need a soft hammer or something to help
jar the housing loose. I would be cautious of trying to pry
it up since it is an aluminum case.
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Front bearing housing being removed |
The exposed oil pump |
Now the transfer case pump is exposed. This pump is what
lubricates the transfer case. The pump should stay on top
of the rear case half as the rear case half is lifted off of the
front half because the pump is connected to a pickup tube
and a screen inside the rear case housing pulling the pump up
can crack the tube or the pump itself . This is actually
a common occurrence and can be avoided by taking a couple of seconds
to be careful with it.
I removed the bolts holding the two case halves together.
I had to find the two slotted areas on the case - there is one
in the upper left hand corner and one in the lower right hand
corner - where I had to place a screwdriver and pry the two case
halves apart. Again, take your time here, as it took me a
good while just to find the slots because on my case they were
filled with RTV and road grime. The case may be stubborn, but
it will come apart.
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The upper corner bolt requires a 12 point
socket, while all of the others are normal hex bolts |
Notice the "pry" notch just above the tab
located next to the 12 point bolt |
Once I had the case halves separated I removed the spring from
the top of the mode fork. The JB Instructions now tell you
to lift the main shaft assembly out of the case, but what they don't
tell you is that you have to remove the front yoke from the front
side output shaft before you can lift the assembly out. I'm
sure this is a simple oversight, but it could cause some minor
frustration in the field (JB assures me this oversight will be
fixed in the next pass of their instructions).
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The front yoke must be removed to complete
the installation |
In order to remove the front yoke you will either need a impact
wrench and socket or you will need to set the unit on the floor
or have someone hold it and use a breaker bar. This nut
will most likely be extremely difficult to remove because it is
torqued 130 ft. lbs.
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A drastic comparison of the JB rear housing (left)
to the Currie rear assembly |
Even here with the yoke set in place it is
still shorter than the Currie assembly with no yoke |
Once you have the front yoke removed, the assembly will be easy
to remove, although I simply lifted mine up just enough to remove
the chain and set the shafts back down. This provided a good
place to hold them while I worked on the next few steps. I
did remove it completely to lube the shift rod and internal
components for the final assembly.
Using a pair of flat snap ring pliers I removed the large retaining
ring on the top of the main shaft. This allowed me
to slide the hub and the sprocket assemblies off of the shaft.
This is well-documented in the JB instructions and I won't duplicate
that here. In our case we did not reuse the sprocket because
we received a new one with the Wide Chain Kit.
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The new "wide" chain is shown underneath for comparison |
The shorter, thicker shaft is the JB Super
Short 32 spline shaft |
I put the sprocket and the hub on the new JB Conversions 32
spline shaft and installed the new retaining ring that came with the
kit.
Note: If your sprocket had needle bearings do not reinstall
them. Per New Process design on the 32 spline shaft these
needle bearings are no longer needed and the assembly will
function just fine without them. Our shaft did not have any
needle bearings to contend with.
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On the right is the new front output shaft
and sprocket |
I installed the main shaft and the shift fork back into the front
half of the transfer case then looped the chain (in my case the
new wide chain) around the sprocket that is part of the front
output shaft (or the new front output shaft in my case) and the
main sprocket. I then lowered the front output shaft into the
front bearing cavity. This required a little patience to
get it lined up - especially with the new chain, but it finally slid into place.
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The internal parts have all been replaced |
Be sure to reinstall the shift mode fork
spring you removed when following the JB Instructions |
I replaced the large spring that I had removed from the top of the mode
fork. That was it for the internal portion and it was time
to put the case back together. At this point, I inspected the pump and the pump screen for problems (perhaps
this should have been done right after I got the case apart).
In my case, we found an issue that needed to be corrected. The screen
was plugged with debris and silicone from a previous repair. I
can only assume that it was installed incorrectly, with too much
silicone when the original Currie Kit was installed in 1997.
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The screen in my 231 wasn't doing much |
I got a new screen for a couple of bucks |
I replaced the screen and purchased a new o-ring for
the seal between the pump and the pickup tube. It's probably
a good idea to inspect and perhaps replace these pieces anyway
since they are relatively low cost and you already have the case
open. It seems like good insurance to me.
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Remove any old gasket material before
reinstalling the pump and part |
Be sure to install a new o-ring. Coat it
with ATF before you press it home |
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This is what the rear case should look
like with the oil pump back in place |
Slinger, pickup tube and screen assembly
inside the rear case |
Once you have the back half of the case put together it should
look like this. The pump sits on the outside and the tube
connects to it on the bottom. Also, I made sure to clean off
the magnet and place it back in its slot in the case.
Then I applied a nice bead of RTV around the entire surface of the
case, putting some water on my finger kept
the silicone from sticking to me (this is a good trick to know if
you choose to use your finger to smooth the bead around the entire
surface).
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Removing the magnet to clean it |
Reinstall the magnet in the slot. It
should fit snugly |
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Applying an even bead of RTV |
Smooth the RTV before joining the case
halves |
I gently installed the back half of the case onto the front half.
I did encounter a little trouble getting the splines on the pump
to line up with the splines on the shafts. It was somewhat tricky,
but with a little patience it slipped right into place.
You may also need to tap the area around where the shift rod protrudes
through the back half of the case in order to get the case half
to seat all the way down.
I installed a couple of bolts
at opposite corners and then spun the output shaft to make sure
everything spun freely and nothing was binding. I then re-installed
the front output yoke, without torquing it down just yet, but
snugged it up good and tight.
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Gently mate the two halves together |
Tighten all the nuts and replace the wire
looms |
I put the rest of the bolts in the case half and tightened them down.
Be sure to remember to replace the cable hold-downs on the
proper bolts so that you can route the wiring back to the same
points it was connected to before.
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I cannot stress enough the importance of
properly torquing all the bolts down to factory specs. |
Once again, I checked to make sure that everything was spinning freely. Other than a slight drag, the shafts should spin and not be
"locked" in place.
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Tone ring installs with the indented side
away from the transfer case |
The side that butts up against the pump is
smooth |
Now that I had the two halves put back together, I slid the
tone ring down onto the main shaft. Be sure to place the tone ring correctly, with the indented side facing out. It
will not work properly if it is installed backward.
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Tone ring sitting down properly against
the pump |
Note: What is a tone ring you might ask? A tone ring is
just what it sounds like. It is a ring that spins and allows an
electronic sensor to count the number of slots or groves that pass by during each rotation. By knowing the circumference of the ring and the distance
between the grooves it can be used to count RPMs. The
RPM or
"count" is used to send an electronic signal to the vehicle ECM
which is then used to calculate speed so you get an accurate
reading on the speedometer. Tone rings are commonly used in ABS
systems, speedometers, fuel injection and cruise control devices.
JB Conversions has custom-built a tone ring that will provide
a stock input signal to your vehicle's ECM. This tone ring
and sensor replace the mechanical speedometer sensor used on
the stock 231 transfer case. JB has adjusted the tone ring/sensor combo to emulate the gearing of 4.10
gears with 31" tall tires, which is commonly found on the Jeep Rubicon.
I prepared the new rear bearing housing by applying a thin layer of
grease to the lip of the new seal and, in my case, I also applied a
thin layer of silicon to the edges of the housing. Be careful
not to block or load up a lot of silicon in the area that extends
over the shift rod. I slid the new rear bearing housing
over the main shaft and bolted it into place. I made sure
that the bolts were torqued down to 30 ft. lbs.
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Applying grease to the rear seal before installation |
Running a bead of RTV around the edge of the
rear housing |
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Rear housing bolts torged to 30 ft. lbs. |
Now that I had the case back together it was time to put the
yoke on. This part became tricky. In fact, I made a
mistake here that forced me to have to pull my rear driveshaft
later on (but I will get to that momentarily).
First, I installed the rubber star washer, then applied a layer of
silicon to the nut and the threads. This will keep any fluid
that seeps through on the spline at bay. I start the nut by
hand and then drive it down with an impact socket. The
instructions tell you to toque it to 180 ft lbs. but I don't think
many "home" mechanics have that setting on their torque wrench.
A trick here may be to reinstall the transfer case in the vehicle
and then torque the yoke nut down (on both the front and rear output
shafts).
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Rubber star washer in place |
RTV the nut and the threads |
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Use an air impact to install the nut.
Must be torqued to 180 ft. lbs |
Rear housing and yoke installed. |
Once the yoke was in place, I installed the new speedometer sensor into the
housing. It should fit easily and not bind. It has a
plastic clip that allow it to connect to the OEM wire loom bolted
to the top of the case.
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Install a layer of ATF on the o-ring
before it is installed |
New electronic speedometer harness
installed and connected to the OEM loom |
Once again I checked to make sure that everything was spinning
freely. Other than a slight drag the shafts should spin and not
be "locked" in place.
After the final check, I reinstalled the transfer case back into
my Jeep, filled it with the proper fluid (in the case of the NP
231 it uses Chrysler ATF), installed the front shafts and plugged
the electrical connection back together. You will notice
that the new electronic speed controller plugs nicely into the
factory harness on the back of the transfer case. If you
have your rear driveshaft go ahead and install it at this time,
as well.
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The finished product |
On the jack and being slid back under the
jeep |
In my case, because of the height of my Jeep, the age of my rear
driveline and the design of the older Currie Kit that used a flange
instead of a yoke, I opted to order a new rear shaft from JB Conversions.
In order to get it measured properly, I waited until the transfer
case was installed back in the Jeep so I could take an exact
measurement, which was 21-1/2" between the yokes (rear output shaft yoke
to the input yoke on my Dana 44). That makes it almost 3"
longer then the shaft I had on there with the Currie Kit.
My shaft was a little over 16" long, plus the 3" of
the flange (which doesn't help with the angle at all), so having
a true ~22" long resting shaft should drop my angles and
increases the life of my u-joints.
An extra bonus was that removing
the shaft from the Currie system required removing 4 bolts from
the flange with very little room to work. The new yoke only
requires removing the 4 bolts that directly hold the u-joint on, which is
a much simpler solution.
The Driveshaft, Testing,
& My Mistake