kit consists of a new sensor, a machined harmonic balancer, sensor
bracket, and necessary hardware. The new sensor’s harness
must be cut and extended to reach its new perch on the front of
This is where
I had the most trouble of the entire swap. The three little wires
that go into the CPS plug do not directly correspond to the 3
little prongs on the opposite side. This little oversight on my
part when I extended the harness led to me getting to practice
my diagnosis skills. 8 hours of practice later, my Jeep was running
again. The only problem I have had with this kit is throwing belts.
Make sure your belt is in good shape, because if you lose a belt,
it will most likely tear the CPS right off of the relocation bracket.
Without the CPS in place, the engine will not run.
thing that is more of an inconvenience than anything, is that
the sensor must be removed and readjusted when the belt is replaced.
This is not a big deal, but it does make what used to be a simple
job kind of a pain.
the engine and transmission were bolted together, the next crisis
I faced was bolting the Jeep NP231 up to the GM transmission.
Fortunately, Advance Adapters had the answer again with another
adapter kit. My application required AA part #50-9102 which is
for a transfer case that was behind an AX-15. The kit differs
based on which transmission and transfer case your vehicle originally
had. It includes a new output shaft, an adapter housing, gasket,
seals, and hardware.
would highly recommend having the output shaft installed by a
professional transmission rebuilder. It is not something that
you want to do in your garage. The adapter housing also includes
a foot to bolt a mount to. You could modify a factory mount to
fit here or use the Advance Adapters part #716008 that is designed
to work with the adapter housing. This kit makes it very easy
to bolt the adapted drivetrain to the stock crossmember/skidplate.
other issue that is encountered when adapting the Jeep transfer
case to just about any transmission is what to do with the shifter.
The stock Jeep transfer case shifter bolts to the shift tower
on the AX-15 transmission. This shift tower left with the stock
unit, leaving nothing for the transfer case shifter to bolt to.
Advance Adapters has another well-thought-out kit to remedy this.
Part #715523 is a kit that allows you to retain the stock transfer
case shifter in nearly the stock location. This minimizes the
floorboard modifications that are necessary.
of the really nice things about the 700R4 is that it is hydraulically-controlled.
This means that it is totally self-contained and requires no computer
to control it. It does require some external inputs but nothing
like today’s computer-controlled drivetrains.
that it requires are a kickdown cable and 12 volts for the torque
converter lock up solenoid. These minimal requirements are another
plus of the 700R4 when it comes to a swap like this.
cable for the 700R4 is necessary for proper operation of the transmission.
It tells the transmission what the throttle position of the engine
is. This allows the transmission to adjust its shift timing, shift
firmness, and passing gear as necessary. Jeep made this part of
the swap easy. The throttle cable bracket on the 4.0L has provisions
for 3 cables running through it. One is for the throttle cable,
one is for cruise control, and the third is for a kickdown cable.
As luck would
have it, Jeep uses the same style of kickdown cable and linkage
on the throttle plate lever as GM. This means plug and play. Advance
Apapters part #716138-KD is actually a GM kickdown cable that
plugs right in to the factory bracket and hooks up to the stock
input that the 700R4 needs is 12 volts for the torque converter
lockup solenoid. A lockup torque converter works like a clutch
for a manual transmission in certain situations. This means that
when you are cruising down the highway at a steady speed, the
torque converter will lock up. The inherent slippage in a torque
converter leads to slightly higher RPM when cruising which means
more fuel burned. When the converter locks up, there is a 1:1
ratio between the crankshaft and the input shaft of the transmission
and that equals better efficiency. The 12 volts that the transmission
sees cannot be there at all times however or the converter would
lock up as soon as the transmission shifted into fourth and would
stay locked up until the transmission down shifted.
solution to this is a lockup bypass kit (AA part #24-60109). This
kit consists of a brake switch, a vacuum switch, wiring harness,
and a new transmission lockup solenoid and harness. When I had
the unit apart to install the Advance Adapters output shaft, I
also installed the new harness. The kit calls for 12 volts to
run through the brake switch, to the vacuum switch, and then to
the transmission. The brake switch opens when the brakes are applied
to unlock the converter. The vacuum switch is open when the manifold
vacuum is low, such as mid to high throttle positions, and closes
with high manifold vacuum, such as when cruising.
is the final step in the process, which will only allow lockup
if the transmission is in 4th gear. All this adds up to lockup
only when the brakes are not on, the throttle is at a relatively
closed position, and the transmission is in 4th gear. Confused
The end result
is a lower cruising RPM on the highway, which is designed to improve
fuel mileage. This is also a very important because if the transmission
is in 4th, the 30% overdrive planetary gears produce a lot of
heat. An unlocked converter also produces a lot of heat. Because
the engine is turning so slowly when the transmission is in 4th,
the fluid flow through the cooler in also very low. The cooler
is able to overcome the heat produced by one or the other but
has difficulty dissipating the heat produced by both. This heat
can lead to premature failure and an angry Jeeper.
The one universal
truth about automatic transmissions is that they produce a lot
of heat. This heat must be dissipated somewhere and typically
in a stock installation, a heat exchanger, or cooler, is located
it the radiator. Because YJ’s were available with an automatic,
a stock radiator is available with a cooler in it. I don’t
think Jeep installed radiators with transmission coolers in all
YJ’s, but mine had one so I flushed it out and threaded
some fittings into it. I bought some 5/16” cooler line and
bent it as necessary to direct the flow from the transmission
to the cooler and back again. I was very careful to route the
lines so that they did not rub against anything that may wear
a hole in them. I also wrapped them in rubber hose where I zip-tied
them together for the same reason. Fluid is the life blood of
an automatic, so I’d hate to lose it because a cooler line
wasn’t adequately protected.
now I’ve made the engine, transmission, and transfer case
all bolt together. I’ve given the transmission all of the
information that GM wants it to have. Now I need to squeeze it
under the Jeep and make it mesh.
The biggest obstacle that you will face with any swap into any
short wheelbase Jeep is rear driveshaft length. The short wheelbase
that we love on tight trails is a curse when modifying these rigs.
I think it goes without saying that a slip yoke eliminator kit
is absolutely necessary for all NP231 owners. Advance Adapters
part# 50-7906 found its way into my transfer case to shave roughly
four inches off of the long NP231 before I decided to install
has a length of 24”. The 700R4 that I replace it with has
a length of 23 3/8”. Then the adapter plate must be added
which was 5/8” and the transfer case adapter is another
1 ½”. This adds up to 25 ½” or 1 ½”
longer than the stock transmission. I was a little concerned about
the rear shaft length because I am running a lot of lift (4.5”)
and plans for a belly up skid plate are in the works. I already
had a home-made 1” motor lift installed in preparation for
the belly up, so I did some more homebrew engineering and decided
to move my engine forward 1” in conjunction with the motor
This was actually
very easy to do with some 2”X1” tubing and a little
time. This was purely experimental but I figured it was an easy
way to relocate the engine and it worked out very well. This gave
me back 1” of rear driveshaft with minimal effort. However,
I wanted more. I always thought more wheelbase would be nice so
I thought I’d do some more experimenting for the sake of
the Jeeping community.
the wedges for the pinion angle on the rear axle to move the rear
axle back 1”. Once again, my homebrew engineering or dumb
luck, one or the other, worked out pretty well. The rear differential
cover rubs the gas tank skidplate slightly when the suspension
compresses, the parking brake cables are a little stretched out,
and the rear of the fenderwells need a little more trimming, but
these are the only issues I have found.
I want to
reiterate that I don’t think the engine and axle relocations
are necessary to put this automatic into my Jeep. I just did them
for experiment’s sake and to make future modifications that
I have planned work well with the new transmission.
The net result
of all of this worked out quite well for me. I thought for sure
that I was going to need new shafts front and rear because of
the difference in length of the transmission. The engine relocation
moved the entire drivetrain forward 1”, while the transmission
is 1 ½” longer. The result was that my transfer case
was ½” further back than stock which would add ½”
to the front shaft length. The rear axle was moved back 1”
which means I actually gained ½” of rear driveshaft
as well. This difference is minimal as far as the driveshafts
were concerned, so I bolted the old ones back in and they have
been working fine.
all fit together pretty well. It wasn’t terribly difficult
to make it fit in the Jeep, either. One thing I was not counting
on was problems with my exhaust system, though. When I was test-fitting
the empty transmission case, I realized that the exhaust was not
going to clear the right side of the case. My exhaust is far from
stock, being rerouted for rock clearance and bigger tubing for
better flow. With this is mind, I can’t say for sure if
a stock exhaust would interfere, but I believe that it would present
the same problem. The solution for me was to cut out the offending
section and have an exhaust shop replace it after everything else
Once the new gearbox was in place, I needed to figure
out how to shift it. Advance Adapters saved me again with a Lokar
shifter. The Lokar shifter bolts to the top of the transmission
and comes up through the floor just like the manual shifter. In
fact, if you just glanced at it, you could easily mistake it for
a manual shifter. It is very well designed and works very well.
It comes with a neutral safety switch and a back up light switch
was a little difficult because the Lokar is designed for a two-wheel
drive transmission and the transfer case adapter interferes with
the location that Lokar intended their shifter to bolt to. More
homebrew engineering on my part was done, and I had it sorted
that the shifter is supposed to bolt to are open on the front
of the transmission flange, so I installed some bolts from the
front side and put the bracket on backwards. I also had to trim
the back of the shifter bracket slightly so I could install the
nuts that hold the transfer case onto the adapter. This was not
the end of it, though. The transfer case shifter bracket had to
be notched to clear the transmission shifter, as well.
All in all,
the Lokar shifter works well. The one thing that I don’t
like about it is the lack of definition between gears. On the
trail, it can be difficult to tell what gear has been selected.
It is also difficult to shift between gears quickly sometimes
because the gates between gears can be confusing as to when the
button on top must be pushed and when to release it. For everyday
driving, this shifter works very well, though.
transfer case shifter, mounted on its aftermarket perch, comes
up through the floor very close to the stock location. It is closer
in my case because I moved my engine forward 1” but even
if I hadn’t, the floor wouldn’t have needed much more
trimming than I had to do.
Adapters bracket for the transfer case shifter angles it toward
the left slightly but not enough to be a problem. This leaning
of the shifter is the only reason I had to trim the floor at all.
The Lokar shifter comes up through the floor about six inches
forward of where the manual shifter came through. For this reason,
the stock tunnel cover cannot be reused. I made a new one out
of sheet metal and was planning on buying some universal shift
boots to cover the holes. Then I remembered that I had the front
half of a stock TJ console in my garage.
After a little
test fitting, Dremel work, and more homebrew engineering, I got
the TJ console to fit. I visited my local Jeep dealer for a boot
and it looks like it is supposed to be there and I now have a
usable cup holder.