Check the trans fuse for 12 volts when the fault occurs. Is the fault intermittant or constant? Does the dash cluster go inop at the same time? GM had a bad batch of ignition switches also pnp switches on the side of the trans. If you have access to a scanner check the indicated gear position compared to the actual gear position. Usually a electrical fault not something internal. Allison built the trans GM sublet the external electronics. Hencho en mexico. :idea: :idea: