91 Suburban Speedometer Not Working

[Rich84]

I installed a '91 cluster in my '86 LQ4/4l80. All the gauges work fine except the Speedo.
As soon as I plugged the harness into the cluster the needle started moving all the way until it is pegged against the Trip knob. When I start the truck the needle moves back down to about 68 mph and stays there.
Do you think I have a bad connection in the cluster somewhere or is the speedo broken.
The temp gauge functions properly except it pegs while starting the truck, then it immediately settles to the proper reading.

[ls1nova71]

Originally Posted by Rich84

I installed a '91 cluster in my '86 LQ4/4l80. All the gauges work fine except the Speedo.
As soon as I plugged the harness into the cluster the needle started moving all the way until it is pegged against the Trip knob. When I start the truck the needle moves back down to about 68 mph and stays there.
Do you think I have a bad connection in the cluster somewhere or is the speedo broken.
The temp gauge functions properly except it pegs while starting the truck, then it immediately settles to the proper reading.

It sounds like something wasn't wired right. Did you re-pin the plug, and if so, are you sure you got it right?

[Rich84]

Yes. I re-pinned the plug. Triple checked everything. I followed the same re pinning matrix that I used on my '84 which works perfectly.