There are no "shifting modules" inside the transmission. As Mr Zimmerman stated, the later units(renamed as 4L60E) used electronic shifting and pressure controls. The module which controls the transmission may be part of the PCM(controls engine and transmission) or a TCM(controls just the transmission). The transmission in this case will contain pressure switches, a torque converter clutch solenoid, shift control solenoids and a duty cycle controlled pressure control solenoid.
The earlier 700R4 and non electronic 4L60 were controlled by a hydraulic valve body and received throttle input, as stated above, from the TV cable. This cable is often mistaken for a "kick down" cable as used in the TH350. The TV cable in the 700 plays a much more important role than simply commanding forced down shift. It is crucial in controlling line pressure to the hydraulic components of the transmission and incorrect adjustment will affect shift behavior and leads to early failure.
The 3-4 clutch pack is a common failure item in this transmission, due mostly to the design of the input drum where the 3-4 clutch resides. The clutch pack installs at the rvery rear of the drum and is held in place by a snap ring. The thin backing plate of the clutch holds back the apply pressure with only the snap ring to keep it in place. The backing plate flexes under this pressure rather than maintain even pressure on the clutches. The clutches slip and burn up.
For years, builders of this unit have tried to work through this, using various hi performance clutch designs. There is a new part available from the Sonnax company named the "Smart Tech input drum that appears to offer a permanent solution to the problem. This is especially important when the unit will be used in a racing or heavy duty application, behind a hi output motor.
There are several other items that affect the 3-4 clutch as well. The 3rd gear accumulator, which is part of the 2nd gear servo assembly, absorbs the shock of the 3-4 clutch apply. The accumulator is a piston with a sealing ring around it. If the sealing ring fails, apply pressure to the clutch will bleed off and the clutch will slip and burn. If the 2nd gear band servo doesn't release quickly enough when 3rd gear applies, the 3-4 clutch pack will burn up. If the trans oil pump doesn't produce sufficient pressure, the clutches will slip and burn. The input shaft is also a conduit for oil pressure from the pump to the various clutches. Sealing rings are used to isolate the circuits from each other. If these sealing rings leak. Pressure will bleed between circuits and cause clutches to slip and burn.