Dakota Digital Universal Electronic Speedometer Interface
it's along name for a fairly simple product. Basically, it
recalibrates the signal coming from the speed sensor to adjust
for changes in gearing and/or tire size. In the
case of the JB Conversions kit, JB set their electronic sensor
and tone ring to emulate the tallest factory tire and gear package
available from Jeep, which is 4.10 gears and roughly 31" tires. This should work
fairly well with a true 35" diameter tire and 4.56"
axle gears, but may be off by a few MPH.
Evidently, my Pro-Comp 35's are entirely too short and as I found
out, my 36" TSL Radials are a smidge too tall to be exactly
accurate without the Dakota Digital device. As many of you know,
the rating on the sidewall is really a guesstimate of the tire
size once it's mounted on a rim and rolling on the pavement (or
dirt, or rock or whatever). Most people could live with
a speedometer that is either 3 mph to slow or too fast, but being
the person I am, I wanted it to read right dead on. So I
opted for the Dakota Digital SGI-5.
Neither Dakota Digital nor JB offer any detailed instructions
for installing this in a Jeep. However, the installation is fairly
simple and should be accomplished in less than an hour
(unless, of course, you are like me and always manage to find
some issue to fix - many times having nothing to do with the project
I am doing). Using the Dakota Digital instructions
(use application #2) and a little common sense, this installation
is quite simple, as the hookups to the device are pretty straight
First, I decided on a location that would be easily accessible,
but up out of the weather and out of the grime. The unit is not
sealed and you really wouldn't want it to be submersed or covered
in grease and dirt for long periods of time. I decided
to mount it inside the cab (at the suggestion of Dakota Digital's
Tech Support) and the best place I found was the kick panel on
the driver's side of the interior. I mounted it there behind my
roll cage and it is out of the way, but very accessible if I need
to change the switch settings for any reason (like swapping to
my off-road tires or perhaps completely changing tire sizes in
Then, I looked in my service manual to determine what wire I
needed to splice into for the speedometer signal. I thought
about trying to find the wire going directly to the speedometer
behind the dash but scrubbed that idea when I realized that there were
400 wires packed into the loom going to the back of the unit and
it would be a nightmare to un-tape and sort out. So on to plan
two, which turned out to be quite easy.
The wire coming from the factory speed sensor at the transfer
case was orange and white. I traced that wire to determine
which wire that connected to on the JB Conversions speedometer
harness (it's the yellow on my harness) and I decide to splice
into that wire.
The orange & white wire going
to the sensor on the transfer case is the speed signal
Removing the JB Conversion sensor
Existing grommet on the driver's side
behind the clutch pedal area
The JB Conversion harness with the
yellow wire cut.
I ran two wires from the drivers side floor board, thru an existing
firewall grommet, across the engine side of the firewall to the
wire center in the middle and then followed the wiring loom down to the transfer case. At
that point, I removed the JB Conversions harness and cut the yellow
wire. I attached one of the new wires to the side coming
from the transfer case and the other to the side coming from the
ECM. In layman's terms, I connected one wire to each side of the
wire I just cut.
Reinstalling the sensor with the
new wires attached
All the wiring cleaned up but not
yet covered by wrap
In order to show you how simple this installation is, I chose
not to solder the wires, and instead, used crimp-less connectors
(Posi-Lock) that can be purchased at most auto parts or hardware
stores. The only tools I needed were a wire stripper and
a cutter. I used black wire, but I would recommend using
two different color wires so that you can keep them straight when
you climb back out from underneath.
Going back up to the to the driver's floorboard, I took the
wire coming from the transfer case sensor and attached it to the
SGI-5 where it says "Sig In" and attached the other wire
(the one going to the ECM) to where it says OUT2 (OUT1 and
OUT2 are commonly used for this type of calibration. I actually
saw no major difference in using OUT1 or OUT2 but ultimately used
OUT2 because it was the recommendation made by Dakota Digital
Next, I found a ground wire (or you can run one to ground the
Dakota Device and connected it in a clean fashion, as you will need
to make sure you have a good ground). I was fortunate that
I have a ground screw already installed for my CB and off-road
lights so I installed a crimp-style connector with a hole to pass
a bolt thru and screwed it into the same location as the ground
for my CB and lights. I connected a power wire to the back
of the cigarette lighter which will provided me with easy access
to a "switched" power source (meaning it turns off and
on with the key and is not live all the time). Then I installed
those wires into the appropriate slots on the SGI-5 (power goes
to PWR and the ground wire goes to GND).
Tying into the power wire connector
for the cigarette lighter
Here a quick redraw of the diagram that shows you exactly what
wire to hook up. Remember that "Sig. In" is the
side coming from the transfer case and that OUT2 runs to the Speedometer
Note: The tech department at Dakota Digital said to be sure
you have a good ground that is on the same plain as the signal
ground to the Speedometer sensor. This can be easily checked
by hooking up a volt meter set to ohms and see if the ground
you are connecting to is giving a good reading back to the ground
wire on the Speedometer sensor. In my case I didn't have any
issues and I don't think that you would either, but if you do
have an issue you could simply splice into the ground wire for
the speedometer sensor and use its ground to ground the SGI-5.
This method would require you running more than the two wires
down to the transfer case and it would also require a line tap
(which is easily found at any auto parts store) to the existing
ground for the speedometer sensor.
According to the SGI-5 instructions the dip switches should be
set to the following before the first test drive. This sets
the SGI-5 unit to a 1:1 pass thru so that you have a known place
to begin your adjustments.:
Once you have the switches set I recommend a short test drive
before you tidy everything up (be sure your new wires are not
laying across the exhaust system or near something that might
cut them and make sure the unit and wires do not interfere with your driving). Take the vehicle around the block and make sure
the speedometer is reading approximately where it was reading
before you made any changes. If anything seems different,
relax, take a deep breath and review each of these steps again.
Make sure you have the correct wires going to the correct connectors
on the SGI-5.
Wiring is installed, switches are
set and I'm ready to test it out
If everything seems copasetic then go ahead and tidy things up.
I used wire ties to secure the two new wires I ran to the factory
wiring loom all the way through the engine compartment and right
on down back to the t-case. Another caution I was given by the
guys at Dakota Digital is to be careful about binding the wiring
to tight to each other as this can cause chaffing of the wire
and the signal could bleed across from one wire to the other providing
an erratic reading - basically causing the speedometer to appear
to jump or drop slightly at speed. If you want to clean
things up even more, you cansolder the wire into place and
heat shrink them for years of service (this is something I intend
to do in the future).
In the interior, I placed the Dakota Device in the position I
already had selected. You may need to drill two holes to
mount it. I choose to mount mine using Velcro so I could remove
it easily to make changes or move it to another location if this
one didn't work out. Once I had placed the SGI-5 unit into
position, I used wire ties to get the excess wiring out of the
way so I don't catch it on a foot or anything that might be sharing
its space and bolted my dash and everything back together for
the last time.
Cutting the Velcro pad down to size
Installed behind the roll bar leg
Now you will need a friend with another car or a Radar Gun or
perhaps a GPS unit. Go drive the vehicle in a safe place
and manner up to an actual speed of 60 mph. How will you
know when you have reached 60? Well you will either need
to have a friend with a radio or a cell phone driving around you
to let you know, perhaps you have access to a radar gun (or can
coerce a friendly neighborhood officer to help you out) or do
what I did and mount my GPS and find an open section of roadway.
At 60 MPH on my GPS the speedometer in my Jeep shows approx 63
miles per hour. Using the formula offered in the SGI Instructions
I get a number of .952 (actual speed / speedometer reading
or 60/63). Using this number I see that the switches
2 thru 10, which are used for the calibration adjustment, must
be changed. Now at 60 MPH my speedometer is pretty much dead on.
Adjusting the switches for the Pro-Comp
Tires and 4.56 gears
Once I put
my off-road tires on I zeroed the Dakota Digital out again by
turning switches 8 and 9 back on and driving it. I discovered
that with these tires, which are much taller then the Pro-Comps,
I read 60 MPH on the Speedo but am actually running ~62
MPH (yeah big whoop but same can be applied to much larger tires ,
as well). Using the Dakota Digital formula of 62/60 (actual
speed/ speedometer reading) I got a reading of 1.03.
Then I looked at the chart and knew that I need to change the
switches to match this chart. Now my speedometer reads correctly
for my off-road tires, as well.
Wow! That is usually the comment I get when I show others
how incredibly short the 231 transfer case in my Jeep is.
When I tell them the riding length of the rear shaft is over 21"
they want to know how it was done. Compared to the usual
12" to 19" drive shafts that people are using, this
The installation was really easy and simple and really just requires
some time and patience to make sure all the parts are installed
correctly - including making sure that everything it torqued
to the proper specs.
The Dakota Digital device also works well and is easy to install.
The hardest part is finding the location and running the two or
three wires you will need to make the hook-ups. However,
the hook-ups can be completed with common auto parts crimp-less
or crimp type connectors and should provide years of fault free
The support from both JB Conversions and Dakota Digital where
outstanding and both had answers for me when I called without
having to call me back or put me on hold for any length of time
(and I will point out that if the instructions are followed, one
may never evenneed to call them).
I am satisfied with this kit and believe that for the for the
money (approx $100 more than a regular Heavy Duty SYE Kit) it is
the only way to go. It will allow
me to make many changes over the next few years without having
to worry about vibrations or angles and with the 32 spline output
shaft and wider chain and sprocket(s) I won't have to worry about
breaking it, either.
The entire solution from JB gives me the confidence that my 231
is beefy enough to run bigger tires, agile enough to maintain
the proper u-joint angles and that my speedometer is accurate
enough to avoid tickets. It also means that my whole setup is adjustable should
I decide to move up to 38" tires or swap my lift for something
else or decide to change my axles or gears.
Pagan is a staff writer for ROCKCRAWLER.com as well as
Our Land Use Editor. Shawn resides north of Houston, TX.
Shawn at firstname.lastname@example.org