VSS Speedo Problem

[pvkj454]

I used a 89 Suburban gauge cluster with the electronic speedo and the transfer case is a NP241 from a Blazer that has the 2 wire VSS sensor for my build. http://67-72chevytrucks.com/vboard/s...d.php?t=404146

I connected the purple wire of the VSS sensor to the speedo input on the cluster and the other to the cluster ground. The speedo will peg out at over 85 mph when the truck is moving and drop back to zero when stopped. I tried swapping the wires at the VSS sensor and it made no difference.

Any ideas? Thanks.