Do you have any info on the rebuild? Could a set of straight cut timing gears have been installed?
Thank you Paul. This is my best guess at the moment. If you notice from the two videos the sound is much more prevelant when standing on the side of the car rather than in front of the engine compartment.If that isn't a gear drive timing set then I would start by checking the fluid level of the transmission with the engine idling in Park. The pump can make that noise if it is worn or if the outer gear is installed backwards. If the filter is plugged it can cause a similar noise. Service the transmission using a new filter/strainer and type "F" fluid.