Electronic speedometer help! 91 Blazer cluster (5.3/4l60e)

[nucknoel89]

Hi all, my 81 has been running great since the swap except for one thing...my speedometer doesn't work!  I got the 91 Blazer cluster but I must have the speedometer wired wrong cause it doesn't do anything.  From what I remember from wiring it up, it has 3 connections: a shared positive, a shared ground, and then the speed signal (which I believe is wire 18 on the plug.)  The way I have it now, that speed signal is coming from the PCM (pin 50 on connector C2).  Is this wrong?  Has anyone else used a Blazer cluster with the electronic trans and what did you do to make it work?

[VileZambonie]

Where's the DRAC?

[nucknoel89]

Where's the DRAC?

What's a DRAC?  Seeing as I don't know what it is maybe that's my problem lol

[Irish_Alley]

http://www.tbichips.com/drac/

[nucknoel89]

http://www.tbichips.com/drac/

After looking at that it sounds like the DRAC is a unit that reads the signal from the speed sensor and then sends a signal to the speedo based on gear ratio and tire size.  But I had that crap programmed into my PCM (03 5.3 Vortec) so I figured the computer did that kind of work.  Or do I still need a DRAC?

[VileZambonie]

So you are running a 5.3L PCM? What year is the PCM and harness from?

[nucknoel89]

So you are running a 5.3L PCM? What year is the PCM and harness from?

The PCM and harness are from a 2003, and they are original to the engine.  And when I had it reprogrammed the guy put in the correct gear ratio, tire size, etc. for me.