Q: Transmission or transfer case grinding when shifting from park to drive/reverse. Truck jerks with it.

Be sure the fluid level is correct. Low (or high) fluid will cause all kinds of transmission malfunctions. If the fluid level is OK, check the bottom of the transmission oil pan (inc. magnet, if installed) and the filter screen for metal particles. If you were parked on an incline, it’s possible that shifting out of park damaged the parking pawl but such wouldn’t necessarily explain the delayed shifting. If you are presently experiencing delayed movement (delayed shifting into drive), that is either a hydraulic control fault (valve body, passages, etc.) or is due to a fault in a clutch pack/clutch piston. External pressure tests can provide some clues. When you shift into drive, a specified pressure should be achieved at the test port on a pressure gauge (or viewable on a scan tool). The exact cause of what you are describing is only going to be determined in an on-site diagnostic, but if you find metal in the pan or suspended in the fluid (the grinding noise is not a good sign), the usual advice is to remove the transmission and refurbish it. If you request a transmission shift diagnostic, the responding certified mechanic will pinpoint the fault and explain your repair options. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.