The ATSG rebuild manual is a must have if you are going to disassemble the unit. I will tell you that there is great information available for this transmission. If you don't understand what these things are, you probably aren't ready to dig into the 700R4. The first thing I would check would be the 1-2 shift valve train, next would be the modulated up shift valve. If the governor checks out, you will need to remove the pan and valve body to check for a stuck valve or valves. If the gov gear is okay, check the valve for sticking. Look for the plastic gear to be stripped. With the cover off, the governor pulls straight out. I use a pair of dust cover pliers that remove the cover without damaging it. You can pull the cover with large channel locks. The governor is under the tin cover on the LH side, towards the rear of the case. If the 700R4 won't shift out of first gear, it's most likely the governor. Pressure will bleed between circuits and cause clutches to slip and burn. Sealing rings are used to isolate the circuits from each other. The input shaft is also a conduit for oil pressure from the pump to the various clutches. If the trans oil pump doesn't produce sufficient pressure, the clutches 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 sealing ring fails, apply pressure to the clutch will bleed off and the clutch will slip and burn. The accumulator is a piston with a sealing ring around it. The 3rd gear accumulator, which is part of the 2nd gear servo assembly, absorbs the shock of the 3-4 clutch apply. There are several other items that affect the 3-4 clutch as well. This is especially important when the unit will be used in a racing or heavy duty application, behind a hi output motor. 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. The clutches slip and burn up.įor years, builders of this unit have tried to work through this, using various hi performance clutch designs. The backing plate flexes under this pressure rather than maintain even pressure on the clutches. The thin backing plate of the clutch holds back the apply pressure with only the snap ring to keep it in place. The clutch pack installs at the rvery rear of the drum and is held in place by a snap ring. 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. 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 TV cable in the 700 plays a much more important role than simply commanding forced down shift. This cable is often mistaken for a "kick down" cable as used in the TH350. 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. 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 module which controls the transmission may be part of the PCM(controls engine and transmission) or a TCM(controls just the transmission). As Mr Zimmerman stated, the later units(renamed as 4L60E) used electronic shifting and pressure controls. There are no "shifting modules" inside the transmission.
I just came across this site and I see the posts are old but decided to add this note in case someone in the future would come here. At times it was not known just what caused the loss of pressure to burn the plates as there are a number of factors involved. I speak from personal experience as we repaired the early model frequently for burned 3-4 clutch plates which is very likely the problem the earlier posters had. The line pressure was now also controlled electronically and enhanced the longivity of this trans. But one of the best changes was when it went to electronic shift control in 1993. The early 700R4 had numerous design changes to make it more robust. The electronic control module will calculate the proper shifts on variations of these two inputs. Now the VSS (vehicle speed sensor) and the TPS (throttle position sensor) are the inputs to the TCM or PCM depending on model year to control shifts. The Governor was for road speed and the TV cable was for throttle input. No longer does it have a TV cable or Governor. In 1993 the trans was redesigned and now has shift solenoids for shift control. Up until 1993 the trans used a TV cable for throttle input to the trans. Being a former Chevrolet Technician I can tell you that is a common failure on the early model 700R4.