Electronic speedo?

[John-e Bravada]

I just swapped a 90-91' diesel dash with the electronic speedo. My 6 speed Eaton Fuller has a VSS on the output shaft so I figured I could get a signal from that. I hooked one of the one sensor wires to the gauge signal and the other to ground. Nothing on the gauge. If I tap the ground wire on the bare metal floor pan it makes the needle move... What type of signal does the dash gauge need a ground reference of a 12v reference?

Once I get it working is there any way to adjust it for tire size and gear ratio?

Any help would be appreciated!

 

[John-e Bravada]

Nothing?.... Maybe I should have posted this in the electronics section instead.

 

[oneluckypops]

VSS Has 2 wires that run to the dash, Well in your case your going to need to hook them up to a DRAC Module then to the speedometer.

Anyhow the VSS has a High reference and a Low Reference. Some place on here there is instructions on how to wire up a Drac module.

 

[John-e Bravada]

I'm finally getting back to my lack of speedo issue. I found a DRAC and I bought the dip switch's to hack it. Now I read that the 90-91' dash has a built in DRAC and you can't hack it... I guess the question is can I eliminate it and run the standalone hacked one?

I still have to remove my tone ring and increase the tooth count on it to get with in the range od the DRAC adjustment.

 

[RetroC10Sport]

1988-91 GMT400s have the DRAC built in (and they can be hacked). Squares still have an external DRAC.

 

[John-e Bravada]

1988-91 GMT400s have the DRAC built in (and they can be hacked). Squares still have an external DRAC.

Awesome! Does the built in one look the same as the stand alone once you pull off the rear cover? It's a diesel dash out of a 90'? square Burb with the all electronic speedo. It has the module on the back of the dash like http://www.gmsquarebody.com/forum/attachment.php?attachmentid=7891&stc=1&d=1350195632

 

[RetroC10Sport]

That's for all the speedo electronics.

I haven't cracked one apart to see what the DRAC looks like.

It figures. I put a 1992-94 tach cluster with a separate DRAC in my 1989 stepside and I come across 2 1991 only tach clusters which are way easier to install.

 

[John-e Bravada]

It's out of a Burb so it's a square. You have it listed as a 90-91 cluster in your "Squarebody instrument clusters and speedometer options" thread.

Can you hack that style of built in DRAC? I guess I need to pull my dash back apart and tear the cover off.

 

[John-e Bravada]

I have the fat girl back on the road so I'm back to the cute projects.. the speedo. I found a DRAC unit and I have the DIP switches to solder in. I'm now working on my input ratio = 62260 (" per mile) x 3.214285714(gear ratio) x 16 (pulses per rev) / 97.32 (tire circumference) x ? (128000 for a 40ppr)

So my question is the 128000 is noted for a 40ppr GM speed sensor, can I just divide this by 40 and multiply it by my 16ppr? If so I come up with an input ratio of 0.653955 which I can set the DIP switches to. If not and I have to use the 128000 I can't calibrate to the 0.261582 input ratio per most of the charts.