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Thread: 1990 obs speedo connection

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  1. #1
    Join Date
    Feb 2011
    Location
    Fort Worth Texas
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    143
    I checked and pin 20 & 21 from the pcm are routed to the vss, so at least that part is confirmed. Still not working though. Some guys say it can be done but they dont remember,maybe something will jog their memory. The truck runs great,lots of power and a blast to drive so this speedo thing is not a big crisis when you look at the big picture,but it would be nice if it worked.

  2. #2
    Join Date
    Sep 2011
    Posts
    264
    On my 1994 model, I pulled out the cluster , then pulled the plug that goes into the back of the cluster out from the dash as much as I could, on mine there was 1 wire that came from the DRAC box to the speedo , I clipped that wire and connected it to the wire coming from my harness. I used a stand alone from Nelson, they had the speedo wire labeled on my new harness.. This is the easiest way by pass all the other OEM stuff on the truck IMO

    The Speedometer wire on the plug that goes directly into the harness is LT Blue/Black on my schematic for a 94 model
    Last edited by 1991SSP; 02-08-2013 at 06:31 PM.

  3. #3
    Join Date
    Feb 2011
    Location
    Fort Worth Texas
    Posts
    143
    I also have a Nelson harness and they left me a green and white wire labeled speedo coming from pin#50 on the pcm for me to hook up. Mickeymotormount also mentioned a lt blue and black wire on his 1993 truck so I'll have to pull the cluster and try that. I'm not sure about the drac box that everyone talks about,hell,I dont even know what it is (lol), but I'm not quitting! Thanks.

  4. #4
    Join Date
    Sep 2011
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    264
    By finding the wire on the cluster plug you are bypassing everything and going straight to the speedometer...

  5. #5
    Join Date
    Feb 2011
    Location
    Fort Worth Texas
    Posts
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    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.

  6. #6
    Join Date
    Jan 2010
    Location
    Cedar Park
    Posts
    898
    Thats good to know as my future project is a 89 rcsb, but i was already thinking of going with Autometer gauges since my bro already pulled out the stock cluster.
    2012 Ford F-150 Ecoboost Super Crew 4x4, stock and staying that way.
    2001 chevy green = LS1 stock, 3k stall, 373 posi, tuned by LSX Power in CS TX

  7. #7
    Join Date
    Feb 2011
    Location
    Fort Worth Texas
    Posts
    143
    Just an fyi on the speedway motors speedo. I got mine today and it will not fit as easy as I described in the above post.I will make it work with some cutting and slicing. The spec sheet on the ad says the speedo body is 1.6" deep which is correct, but the mounting studs and backlight make it around 2 3/4" deep. Sorry for the bad info, I should have installed it before I said anything.

  8. #8
    Join Date
    Jul 2009
    Location
    Oklahoma City
    Posts
    152
    Quote Originally Posted by exboatracer View Post
    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?

  9. #9
    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?

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