Don't pull the cluster!
The noise you hear is coming from the vacuum switch over valve for upshift delay.The valve is located under the hood behind the brake booster.
You can verify this as the source by doing the following,unplug the connector from the valve and join the vac. lines togather and road test when cold.
If the noise is gone as I suspect it will be you can either leave it as it is or start looking for the interruption.