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
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.