Drac question?

[Benny1000]

I have a 91 gmc that originally came with sweeper style gauges, the tach quit working then the speedo went out. I tried finding another cluster but it hard to find the proper replacement. I grabbed the clister and drac out of a 93 and wired in the new harness and drac harness. all my gauges seem to work and tach is working, I followed a recalibration formula for the drac and the speedo also seems to work ,but the problem I’m having is that as soon as I get moving maybe 20 kph( Canadian, lol) my torque converter locks up. If you tap the brake it unlocks then locks again.Not sure if there was something I missed or maybe the original vss doesn’t have the same signal? Scratching my head on this one.

 

[GMCTRUCKS]

Maybe because in 1993 the 4L60e is electronic.

 

[DerekTheGreat]

Well this might not be the problem but my '89 service manual states that the speed sensor on the trans sends it's signal to the cluster which then sends it to the ECM.. Did you make sure the ECM is still "seeing" the speed signal?

 

[Benny1000]

I found a different wiring diagram for the drac module, most of them don’t show what the blue wire coming off of the drac is but it is another output signal. I moved my pcm wire over to the blue wire slot and it started working. I think one slot is 2000ppm and the other is a 4000 ppm signal or something like that.

 

[DerekTheGreat]

Cool, so it was that.