Sorry! I missed your last couple of posts, let me answer some questions for you!
Unfortunately, you will have to replace your entire gauge cluster to do this swap easily. While it does bolt right in, it does require you to re-pin the instrument cluster connector. You cannot put an electric speedometer into a regular mechanical drive instrument cluster without doing some serious modifications to it.
When I installed the 1990 cluster in my 85, I used a multimeter and some previous wire coloring knowledge to decide where each pin should go. The newer cluster does not use as many ground / 12V ign power wires as the older clusters do, but uses all the rest of the wires the same way. The extra pins that are freed up by sharing power / grounds are used by the speedometer input, and a couple extra idiot lights that are in the 90 cluster such as a light for the alternator (great for CS130 swaps!).
Just start chasing the imprinted wire paths on the back of the old instrument cluster and see where they run to. Write down which wire feeds which instrument or light in your cluster. Keep in mind that some of the pins which have two wires connected to them of the same color simply go back up into the harness and loop right back around and come back down again to a second pin. Your 90 cluster will not use any of those redundant wires, so you can simply clip the second pin off at the base of the first pin which has both wires run into it.
With a little bit of thinking, and some measuring, you'll find that it is not an overly difficult task. I personally used some of the spare ignition / ground wires left over after the swap was done to power my DRAC, which I mounted just behind the instrument cluster.
Right now, you will have an optical sensor connected to the back of your speedometer head which outputs a 2000 pulse per mile signal that your ECM uses to determine your current speed. The DRAC also has a pin that outputs this same 2000 pulse per mile signal for your ECM to use, another 2000 pulse per mile output for your cruise control, in addition to the 4000 pulse per mile signal used by the speedometer, and another signal used by the ABS system, if so equipped.
The DRAC is a little circuit board that converts the 40 pulse per drive shaft revolution signal generated by the sensor on the tail shaft of the transfer case to the different signals mentioned above for your ECM, Speedometer, cruise control, ABS etc to use. There are several different versions of it, one of which in particular you want to get to be able to easily modify it to allow you to calibrate it for your tire size and gearing.
See this link for more information, and some pictures of a DRAC http://www.tbichips.com/drac/
When you pull the transfer case, just get the wire connectors at the tail shaft, and at the DRAC. the harness for it will be all wrapped up in the main trunk harness of the donor vehicle and would require a ton of effort to remove it intact. It is not very hard to just pull your own wire to install everything yourself, and with some creativity you can remove the terminals from the connectors and solder new wires to them for a nice clean installation, just make sure you protect your new wires well with wire loom and grommets when you pass through the firewall. To wire the DRAC, you'll need a ignition switched power wire, ground wire, signal output wires to your ECM, speedometer, cruise and ABS as require along two wires running down to the sensor in the tail shaft.
Swapping a mechanical NP241 over to an electric NP241 does not involve a main shaft swap. You simply need to take the old mechanical tail shaft off, and remove the big snap ring that retains the drive gear and replace the gear with the tone ring used by the newer electric speedometer. You then need to install an electric tail shaft assembly to complete the swap. Keep in mind that while the sensor is the same on the driver's side drop t-cases, the tail shafts will not interchange with the pass side drop t-cases.
You should not need anything else from the donor vehicle to make it all work, you simply need to make sure that you wind up with a VSS installed in the tail shaft of the t-case you install in your truck, a DRAC, and the electric speedometer cluster. The rest is just wiring!
Unfortunately, you will have to replace your entire gauge cluster to do this swap easily. While it does bolt right in, it does require you to re-pin the instrument cluster connector. You cannot put an electric speedometer into a regular mechanical drive instrument cluster without doing some serious modifications to it.
When I installed the 1990 cluster in my 85, I used a multimeter and some previous wire coloring knowledge to decide where each pin should go. The newer cluster does not use as many ground / 12V ign power wires as the older clusters do, but uses all the rest of the wires the same way. The extra pins that are freed up by sharing power / grounds are used by the speedometer input, and a couple extra idiot lights that are in the 90 cluster such as a light for the alternator (great for CS130 swaps!).
Just start chasing the imprinted wire paths on the back of the old instrument cluster and see where they run to. Write down which wire feeds which instrument or light in your cluster. Keep in mind that some of the pins which have two wires connected to them of the same color simply go back up into the harness and loop right back around and come back down again to a second pin. Your 90 cluster will not use any of those redundant wires, so you can simply clip the second pin off at the base of the first pin which has both wires run into it.
With a little bit of thinking, and some measuring, you'll find that it is not an overly difficult task. I personally used some of the spare ignition / ground wires left over after the swap was done to power my DRAC, which I mounted just behind the instrument cluster.
Right now, you will have an optical sensor connected to the back of your speedometer head which outputs a 2000 pulse per mile signal that your ECM uses to determine your current speed. The DRAC also has a pin that outputs this same 2000 pulse per mile signal for your ECM to use, another 2000 pulse per mile output for your cruise control, in addition to the 4000 pulse per mile signal used by the speedometer, and another signal used by the ABS system, if so equipped.
The DRAC is a little circuit board that converts the 40 pulse per drive shaft revolution signal generated by the sensor on the tail shaft of the transfer case to the different signals mentioned above for your ECM, Speedometer, cruise control, ABS etc to use. There are several different versions of it, one of which in particular you want to get to be able to easily modify it to allow you to calibrate it for your tire size and gearing.
See this link for more information, and some pictures of a DRAC http://www.tbichips.com/drac/
When you pull the transfer case, just get the wire connectors at the tail shaft, and at the DRAC. the harness for it will be all wrapped up in the main trunk harness of the donor vehicle and would require a ton of effort to remove it intact. It is not very hard to just pull your own wire to install everything yourself, and with some creativity you can remove the terminals from the connectors and solder new wires to them for a nice clean installation, just make sure you protect your new wires well with wire loom and grommets when you pass through the firewall. To wire the DRAC, you'll need a ignition switched power wire, ground wire, signal output wires to your ECM, speedometer, cruise and ABS as require along two wires running down to the sensor in the tail shaft.
Swapping a mechanical NP241 over to an electric NP241 does not involve a main shaft swap. You simply need to take the old mechanical tail shaft off, and remove the big snap ring that retains the drive gear and replace the gear with the tone ring used by the newer electric speedometer. You then need to install an electric tail shaft assembly to complete the swap. Keep in mind that while the sensor is the same on the driver's side drop t-cases, the tail shafts will not interchange with the pass side drop t-cases.
You should not need anything else from the donor vehicle to make it all work, you simply need to make sure that you wind up with a VSS installed in the tail shaft of the t-case you install in your truck, a DRAC, and the electric speedometer cluster. The rest is just wiring!
