Question about 1993 GMC Suburban
The 4L80-E transmission uses 2 electric shift solenoids to control transmission upshifts and downshifts. In addition, a force motor (also referred to as pressure control solenoid) controls hydraulic line pressure, and a Torque Converter Clutch (TCC) solenoid controls TCC application. Solenoid is turned on and off by the Powertrain Control Module (PCM) or Transmission Control Module (TCM). PCM/TCM has on-board self-diagnostics to help identify any components or circuits that may need further testing. Shift solenoid holds hydraulic pressure when it is on and releases pressure when it is off. This action controls the shift valves inside valve body. By switching one or both solenoids on or off, different combinations of clutches, sprags and bands are operated.
Models with gasoline engines use a Powertrain Control Module (PCM) computer. Models with diesel engines use a Transmission Control Module (TCM) computer. These computers control TCC, force motor (hydraulic pressure) and shift solenoids "A" and "B".
If your transmission was rebuilt and these solenoids were not replaced. It is likely that one of them is acting up. You should have your computer scanned for trouble codes, there are many autoparts stores like AutoZone and Checkers that do this for FREE, Once you know which solenoid is failing, just remove the tranny's fluid pan, (just like if you where going to change the trans. fluid) and with the diagram I sent you, identify the defective solenoid and replace it. It is a pretty simple job to do, but if you take the vehicle to a shop, you may get ripped off.
I will send you a better copy of this diagram by mail.
Posted on Sep 28, 2010
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Posted on Jan 02, 2017
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