While some of the components
listed were eliminated completely, the functions of others were simply trans- ferred to different components. New hardware for the 4L60E
includes: • Internal Mode Switch (IMS) was added
• Wire harness change • Manual shaft length change • Detent spring • Park rod • Bonded spacer plate • D4 channel changes in the valve body
• New DTCs added The Internal Mode Switch (IMS)
is similar to other GM transmission IMS designs. The IMS is mounted on the manual shaft and changes position as the manual shaft moves. Since we now have an IMS, the design of the manual shaft, detent spring, and the park rod also needed to change (figure 1). The wiring harness update included pin configuration changes because the IMS was added and the 3-2 solenoid was eliminated. The IMS works the same way it
does on other applications, with the IMS providing a binary signal. The TCM/ECM sees a series of high voltage and low voltages (high = system volt- age; low = less than 0.5 volts), depend- ing on whether the internal switches are open or grounded. The sequence
Figure 2
the computer reads indicates the range selected (figure 2). Since they’ve added an IMS, GM
also needed to add DTCs to help diag- nose the IMS. They added seven new DTCs: P1915 – Internal Mode Switch doesn’t indicate park/neutral
P1820 – Internal Mode Switch A (low voltage)
P1822 – Internal Mode Switch B (high voltage)
P1823 – Internal Mode Switch P (low voltage)
P1825 – Internal Mode Switch (invalid range)
P1826 – Internal Mode Switch C (high voltage)
P1915 – Internal mode switch doesn’t indicate P/N during starting
As you can see, the changes to the
4L60E will have an impact on servic- ing these units. The updates weren’t designed by engineering to back-ser- vice earlier units. So the next time you get one of
these 4L60E transmissions in, take a little time and examine these changes, to help you identify the differences. The time you save based on proper com- ponent identification will be money in your pocket. Yes the 4L60E family will be
missed, but like all things in life, change is inevitable. Until next time, remember: opportunity often comes in the form of misfortune or temporary defeat.
GEARS January/February 2012
27
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