This ^^^^^. If the truck has A/C, remove the driver-side A/C duct that crosses under the steering column. With the instrument cluster firmly secured in the dash, while kneeling on the floor use your left hand to reach up behind the cluster from below and wrap your fingers around the cable with your thumb pointing toward the speedometer head. Remove the cable from the speedometer by pushing the spring retaining tab toward the cluster with your left thumb while simultaneously pulling the cable away from the cluster with your left hand.
Removing the pressure tube from the oil gauge can be a PITA. Due to limited accessibility, use a compact open-end wrench that properly fits the tube nut at the gauge attachment. If the gauge has a back-up nut, support it with a wrench when loosening or tightening the line nut. Be careful that you don't overtighten the line nut during subsequent reinstallation. Depending on the configuration, you may find it beneficial to disconnect the pressure tube from the engine first, allowing the tube to slip more freely through the firewall providing additional line slack.
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