1990 obs speedo connection

[tempoffroad]

Post a pic when your done I am doing the same swap in same year truck.

[Venom]

Ok,I pulled the cluster and don't have a blu/wht wire.Didn't think there was one cause I couldn't find one on the schematic. After lots of research (homework you guys gave me lol) I found out that the 1990 trucks dont have the white drac box with the blu/wht wire. It's built into the cluster making the hookup more involved requiring a dakoda digital module or a high dollar reluctor wheel from s&p.Here's what I'm doing--- putting an aftermarket electric speedo from Speedway motors P/n91065051 in place of the stock speedo head which will just unplug from the cluster. I'll make a brushed aluminum face plate and mount the 3 3/8 guage dead center. The body of the guage is 1.6" deep so it will clear the circut board. I like the looks of the guage and also the fact that it will give the dash a different look. Just want to give all who helped me on this,and with my build in general a BIG thankyou. I'd like to shake your hands someday.

Do you have the part number for the dakota digital module to run the 2002 4l60e trans with the 89 stock cluster?

[pmcarbuilder]

seems like there should be a was to use the 1990 speedo work,Im trying to get one going myself,could I just use a cluster from a 1992 c1500 with out rewiring?

[88stepside]

I spent a lot of time on my speedometer cluster when installing the LS1 in my 1988 RCSB. Here is the info on 88-91 speedometers, the cluster has circuits inside that perform the same functions of the DRAC in 92 and later trucks. As in, speedometer driver, speedometer correction, RWAL (antilock brakes), cruise control output, speedometer out to ECM.

88-91 the Yellow and Purple twisted pair wires come off the trans tail VSS and go up the firewall and into large square firewall connector harness near power brake booster. These wires go through connector in firewall and straight into speedometer cluster. The signal the VSS produces is a simple AC square wave signal, the VSS is a magnet reading a toothed ring with 40 teeth, and that 40 pulse signal is what your speedometer needs to work. 88-91 speedometer clusters then condition the VSS raw signal and send it out to everything else, antilock brakes, cruise, original ECM.

If you are using an automatic trans in your swap just jumper off the VSS wires, at trans, at back of speedometer, it doesn't matter, and run them to your new ecm. I don't know why you would though, usually all your new ECM needs to know is if you are moving or stopped. The speedometer output from back of cluster that went to old ECM can be run to new ECM speedometer input pin. Your new ECM is not controlling cruise, antilock brake, or speedometer, as those functions are retained in original cluster if you uncap the yellow and purple wire and run them back up to firewall connector, twist the as they were originally to suppress any noise.

[88stepside]

seems like there should be a was to use the 1990 speedo work,Im trying to get one going myself,could I just use a cluster from a 1992 c1500 with out rewiring?

This was a popular swap back when everyone wanted to get rid of their moonie gauges. It does require the cluster connector and pigtail from a 92 or newer truck, cutting the pocket that the cluster fits into, and repining a few wires at rear of cluster. And also, make sure to grab that DRAC module from the 92 because all the functions that are in the 88-91 cluster will now be in the DRAC module, speedometer correction included.
You will still have an 85MPH speedo and 5000RPM tach when finished.

[88stepside]

1988 VSS wiring diagram- brown/ white turns to brown through a connector