jfg455

iTrader: (5)

I swapped an 04 LM7 (5.3L) and a 2WD 4L60E into my 1990 chevy RCSB C1500. I used the 04 truck harness and just modified what I needed for powers and grounds etc.
My question is this:
the stock 90 speedo has the same 4K pulses per mile as the output speed sensor in the 4L60E. If you hook the speedo to the sensor it works fine. If you hook the speed sensor up to the factory 04 harness and PCM it reads fine in the PCM. If you try and splice the 90 speedo harness into the output speed sensor circuits (with the PCM still hooked into it) niether will work. Has anyone run into this and did they find a cure? diodes in line maybe or is it just too much resistance for either to work correctly? Thanks in advance.

ls1nova71

iTrader: (4)

I've had that problem with other speedometers. Have you tried hooking it up to the speedo output from the PCM, on C2-50, dark green and white wire?

jfg455

iTrader: (5)

I had not thought of that. I will check into the schematics and see if it is still the same 4K pulses coming out of the PCM. Thanks for the input.

I checked on the GM SI and this is what it said:

Speedometer
The instrument panel cluster (IPC) displays the vehicle speed on the analog speedometer based on the vehicle speed signal from the powertrain control module (PCM). The PCM converts the data from the vehicle speed sensor to a 4,000 pulses/mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed.

The speedometer defaults to 0 km/h (0 mph) if a malfunction in the vehicle speed signal circuit exists.

so it looks like that will work. Thanks.

ls1nova71

iTrader: (4)

Yes the PCM out puts 4000ppm to the speedometer. Just don't use the one that goes to the ABS, it's not 4k.

jfg455

iTrader: (5)

I checked some other years an 88-91 has the DRAC built into the cluster. the 92-94 clusters had a seperate DRAC module. So it seems to me that I can use a 92-94 cluster and just run the 04 speedo output to the new cluster input and be good. I think I have a 92-94 cluster that I will try it on. Or I could bypass the DRAC in the 90 cluster.

fiveg1

what did u use t get it to work

1967camaro78

iTrader: (1)

I am interested too about to do 6.0 swap in my 89 c1500. I have 1994 cluster in it now and picked up a drac from wrecking yard

jfg455

iTrader: (5)

So to up date an old thread I finished another swap this time in a 92 C2500 ext cab. I put in an 01 LQ4 / 4L80E in it with an LS9 cam and springs. For the speedo I spliced the truck side VSS wires into the ls harness but you have to reverse the wire colors. The 01 has the ppl/blk wire as the high signal and the 92-94 has the ppl/blk wire as the low signal. Swap them and everything is happy

Brumby

Hi. I put a 2005 LS1 and 4L60 into my 1989 GMC C1500. If hooking into the speedo output from PCM, which wire do I hook in? there is a yellow and a brown and white from the old TH700 VSS. What about the spare wire? Where does it go? Thanks very much

THEFERMANATOR

88-early 91 used the moonie cluster. It has the drac built into the cluster. The 2 wires from the speed sensor run straight to the cluster, it converts it to run the speedo, and has a 2k ppm output for the ECM and cruise control. The LS ECM's output a 4k ppm signal to the cluster. If you swap to a late 91-94 cluster, you can run the LS ECM's speedo signal straight to the cluster.

Brumby

Thanks very much. I don't think changing out the cluster is really an option. This truck is my daily driver and I'm in Australia, where these things are rare as hen's teeth. Is there another way? Maybe a way to amplify the signal from 2 to 4K?

Brumby

Just further to my previous comment - I guess us Aussies have a slightly different understanding of things than you guys in the US - when you mention "cluster", you mean gauges? Do later model (up to 94) gauges fit straight in where the old ones are and work? If that's all it is, that would not be too difficult at all...if I can source a 91 to 94 set of gauges

THEFERMANATOR

Yes, cluster refers to the gauge cluster. For left hand drive vehicles here in the states the cluster is a pretty straight forward swap. I believe you have to change the wires from the old plug to the new style plug and add in a vehicle speed sensor buffer. Since you're installing a combo that doesn't need a vssb since your ECM outputs the signals, it is not needed. I mention left hand drive because I know most of these trucks in Australia were converted to right hand drive and used a hybrid S10 dash. So the cluster swap may not be as straight forward.

The early moonie cluster ran the speed sensor wires straight to the cluster and the drac(the part that converts the raw sensor signal to the required pulse per mile outputs) was built into the actual gauge cluster. So there is no speed signal input to it since it has the drac/vssb built in. For the LS the speed sensor wires run straight to it.

So the big question is, is yours a left or right hand drive, and which cluster does it have in it. You may be able to splice the speed sensor signal and run it to both the cluster and ECM and see if it will work that way.

Brumby

Great. Thanks so much for your time. My truck is stock standard lhd - never been converted. I did have the wires from the old VSS spliced into the loom at the 4L60 VSS. The speedo just sat at 0. Then I swapped the wires and the engine ran like ****. I guess it messed up the speed signal to the ECM.
So basically, from what I understand here, I should be able to fit a 94 cluster, plug it straight into the spot where the old cluster is, splice the wires from VSS back in and it should work? I am a bit unclear on what you're saying near the beginning - would I have to change the plug and add a buffer if my truck has been converted, or if it is stock LHD?

THEFERMANATOR

You can get a 92-94 cluster, I believe 93-94 you could get them with a tachometer. Change the plug to the one for the new style cluster, then use the speedometer output from your LS ECM to run the 92-94 cluster. You won't need the vssb since the LS ECM does what it would do.

ls1nova71

iTrader: (4)

If you need a newer cluster, I can get you one, they're about $40 around here. Not sure how much it would cost to ship it to Oz though, but like you say, probably hard to find one already there. What part of Australia are you in?

Brumby

Thanks so much for your help guys. I have actually just found a gadget, that should allow me to use my original equipment. I haven't ordered it yet, but will update you when I get it working. Its from Dakotadigital.com and the gadget is called a SGI-5E. Here is the link, in case it will be of use to you at some point. Looks like a pretty versatile gadget https://www.dakotadigital.com/index....rod/prd126.htm
Best Regards from down under
Tom

THEFERMANATOR

I would contact them before you buy that. It appears to do the same exact thing as a VSSB does, but that does you no good in splitting your speed sensor signal since both your ECM and gauge cluster both require a raw A/C signal from a 2 wire magnetic speed sensor. That box is designed to take a raw A/C voltage speed sensor output and convert it into a 5 volt DC square wave output.

Brumby

I finally got my speedo working properly after sorting some harness issues. The Dakota Digital SGI-100BT is doing the job by converting the 4000PPM signal to a 2000PPM signal. It can do a lot more conversions and applications. Great gadget

Harryinnh

I bought the SGI-100BT based upon your success. However I can't figure it out. I found the yellow and purple wires going to the instrument panel. And I think I have the device configured correctly.

Any help you could provide would be appreciated !!