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When you examine this valve body (see Figure 2), you see the many “L” retainers. These locate and hold plugs, which separate and seal oil circuits. As the valves toggle, the plugs become loose and allow fluid to pass around them. In the past, some end plugs could be ridged or knurled to reduce oil loss, but in this casting, it’s not possible, due to their depth in the bore and the close fitting tolerances. In newer versions, plugs are anodized and cannot be altered. As these toggle, they wear the casting and not the plug.
Besides the plug and retainer issues, bore wear, as illustrated in the product announcements in this catalog and indicated by the arrows in Figure 4, add to the complaints. With the interdependence of circuits on overall control, it’s not practical to patch-fix this body.
There are other reasons why a transmission won’t shift, but these are the three biggest ones. A transmission problem is not something that can or should be ignored, so if you find that your automatic transmission isn’t shifting properly, take a look at the fluid levels and get it to a mechanic as quickly as possible. My Automatic Transmission Won't Shift Into 2nd Gear by Robert Morello. Automatic transmissions perform all of the tasks normally done by the driver in a car with a manual transmission. They shift up and down as needed, return the engine to neutral when at rest, and clutch through each step along the way. Modern cars have computerized.
For example, delayed engagement is not related to the TCC regulator valve and high TCC slip is not fixed by enlarging a line-to-lube hole. Modifying valve control generally results in shift quality that will not meet customer expectations.
A TCC modulator valve that will not stroke or may have partial stroke can be diagnosed on a road test. The SonnaFlow® must be installed and converter fluid must reach 150 degrees Fahrenheit before the thermal element opens, allowing for external cooler flow. Flow will increase from an average of 1.4 GPM with TCC off, to 2.3 GPM-plus under full apply. The scanner should be used during this drive to monitor TCC duty cycle percentage. As modulation increases to 50%, the solenoid should have fully stroked the TCC modulator valve. When you see the sharp rise in GPM on the SonnaFlow®, the valve has fully stroked. If cooler flow does not rise as TCC apply is commanded or the engine stalls upon forward engagement, inspect the TCC solenoid first.
If the engine stalls forward and reverse, look for blown gaskets, a worn pressure regulator bore (which you can replace with ) and then pump or converter issues. The coast clutch shift valve lives in the same bore as the TCC regulator. The CCS is not modulated, but controlled as an on-and-off valve by the SSD/CCS solenoid. When this bore is worn, the solenoid oil flows around it, resulting in the loss of overdrive servo release pressure. This results in no 4th in a 4R or no 2nd and 5th in the 5R unit. If it sticks, the coast clutch will not apply. This wear can be found on a hydraulic test bench or with the Wet Air Test in Figure 6.
Fluid coming out of the channel indicated by the pen tip indicates leakage in the Coast Clutch valve circuit. Valve bore wear may occur at low service use, depending on driving conditions. The two modulated circuits of TCC and EPC should always be inspected due to their valve activity. Now, the question: Install a specific repair or perform a complete rebuild? That decision is ultimately yours, as you forecast how long a marginal bore may last.
A repair for longevity requires tooling. The process creates contamination, so it’s best to strip the entire casting. We supply various tips that, with practice, will help you to dismantle one in less than 20 minutes.