Problem: The customer brought the truck in because of a long delay when engaging transmission into first gear after sitting overnight.
Details: Upon recommendation of the Tech-Assist consultant, the technician inspected the check valve ball and spring located in the automatic transmission cooler line. He found that the check valve was not sealing properly.
Confirmed Repair: The technician replaced the oil cooler line, which including the check valve and the problem was resolved.
Diagnostic strategy: The converter drain-back check valve is located in the TOC pressure-supply line, between the engine mounted transmission oil cooler and the transmission oil cooler. The valve prevents fluid from draining from the converter into the cooler and lines when the vehicle is shut down for lengthy periods. If the check valve is defective, the oil will drain back into the oil pan causing delay when engaging the transmission for the first time in the morning.