91 cluster swap issues?

[mr.griz]

Hey guys i did the swap 91 moonies to 91 with tach, but now when i data log (trying to burn my own chips) with winaldl the speedo on the software reads speeds way out of whck to what my truck is doing, and even when it it idling it reads speeds like as if it was moving. When driving the torque converter is locking when it is not supposed to because the speed is reading wrong. The actual speedo is always reading correctly. So i took the cluster back and got a different 91 cluster and now it is doing the same thing. This does not do it all the time, but quite a bit. How do i trouble shoot this to see what is causing the funky readout.

Thanks