1990 obs speedo connection

[Mickeymotormount]

Yes, my VSS wires go to the PCM. Without it, the PCM doesn't have any referencing speed signal coming from the vehicle. I also have the DRAC box behind the glove box and ended up jumping the wire from the Cruise control right to the speedometer wire, thus bypassing the DRAC box. I was having Cruise control issues and it ended up being the '99 cruise control box that I got from the Silverado 6.0 donor vehicle was junk. I just ended up using my '93 cruise control box and switched out the cable from the '99 box so it would reach the throttle/air valve at the front of the engine.

[exboatracer]

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.

[1991SSP]

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

[exboatracer]

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.

[1991SSP]

By finding the wire on the cluster plug you are bypassing everything and going straight to the speedometer...

[exboatracer]

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.

[GraniteBlueNNBS]

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.

[exboatracer]

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.

[Mickeymotormount]

Can't you update to a later guage package? I have a couple that I'm not using and would be glad to help out. They're out of a 94 model with factory tach. It may be alot easier than hacking up your dash.
I'm sure there are differences in the wiring, but nothing too complicated.

[exboatracer]

Thanks for your kind offer to help out.Your idea is probably the way to go,but now I have this speedo and want to make this work.I have a spare cluster on my bench and I'm trimming some plastic so the new speedo will set down a bit more and clear everything. Thanks again.