When the GM 4L60-E family of transmissions evolved from the 700-R4, the overrun clutch is no longer applied in 1st and 2nd when accelerating from a stop in D3 shifter position. This change was made to improve coastdown drivability in D3 but had the side effect of reducing the torque capacity of the input section.

For greatly improved input sprag and Forward clutch durability, Sonnax drop-in, heavy duty 2-3 shift valve 77754-41 for 4L60-E, 4L65-E and 4L70-E units will apply the overrun clutch in D3 1st, 2nd and 3rd Gears.

• Improves input sprag and Forward clutch durability
• Critical upgrade for all heavy-duty and performance vehicles
• Drop-in Zip Valve™ parts install quickly and easily