In GM 4T65-E units, continuous oscillation of the converter apply valve in the cast-aluminum bore causes bore wear, particularly at the TCC signal valve spool closest to the solenoid. Wear in this area allows TCC signal oil to leak, which inhibits the valve from stroking to the lockup position. Due to the valve body casting design and oil flow, this valve is also subject to extreme side loading, which increases the wear rate. Early OE versions of this valve were made from non-anodized aluminum, and show significant wear marks.

• Hardcoat anodized aluminum valve with an expandable PTFE seal on the TCC signal valve spool provides a positive seal to ensure proper stroking of the valve
• The most inward Sonnax valve spool is almost 2.5 times longer then the OE spool, creating more valve-to-bore sealing area
• Greater sealing area combined with annular grooves allows the valve to stay centered in the bore and prevents side loading
• A replacement O-ring has been included for the OE end plug, to be used after inspecting the TCC regulated apply valve
• Drop-in Zip Valve™ parts install quickly and easily