4L60E TCC Regulator and Isolator Valve Kit 77754-04K

This is the Sonnax 77754-04K TCC regulator and isolator valve kit for GM 4L60E, 4L65E and 4L70E valve bodies. It contains four pieces: a lengthened isolator valve, the spring, a hardcoat-anodized aluminum regulator valve and a wear-resistant aluminum regulator sleeve. The sleeve renews the worn section of the bore, and the longer isolator valve rides in the unworn part of the bore. Annular grooves on the valves keep them centered so the new parts do not side-load and wear the bore out again.

On a high-mileage 4L60E the TCC regulator and isolator bore wears oval and bleeds off converter apply oil. That shows up as converter clutch slip and TCC slip codes such as P0741 or P1870, a hot converter, low line pressure, harsh 1-2 shifts and, if it is left alone, a burned 3-4 clutch pack. A new converter or solenoid will not fix it when the leak is in the bore, which is why a vacuum test of this circuit belongs in every 4L60E valve body rebuild.

On the bench, pull the valve body, remove the retainer and the factory isolator valve, spring and regulator valve, then vacuum test the bore to confirm the wear. The bore has to be reamed to accept the sleeve, and the reamer and install tooling are sold separately, so have them on hand before you tear the valve body down. Install the sleeve, regulator valve, spring and isolator valve in order, reinstall the retainer and vacuum test the circuit again before the valve body goes back on the case. Confirm your valve body casting and year before ordering.