I just installed a motor and transmission from my daughters 2005 Vibe that she wrecked (low miles) into another 2005 Vibe that I picked up. After completing the install, it started right up and ran great with no check engine light, or any other warning lights. On the first drive I experienced an issue with the speedometer dropping a few miles per hour, then returning to the correct speed. It did this every few seconds and the car surged when it did it. I noticed that the new motor had a VSS sensor on the transmission and the old one did not. I replaced the ECM from the wrecked car into the new car since it matched the drivetrain. The same result except it was a longer time between fluctuations. Still no warning lights or check engine light. The car has ASB and the old one did not. Any ideas where I go from here? Thanks in advance for any help!