4L60E, 4L65E, 4L70E

Warning:
Casting hardness often causes adverse issues with reamer performance in the 4L60/E pump. For consistent bore finish quality and extended reamer life, recommend using Sonnax carbide tool kit 77917-TLC. This tool kit can also be used with Sonnax oversized pressure regulator valve 77917-06.

Symptoms:

• Erratic line pressure
• Low line rise
• 3-4 Clutch failure
• Excess pump noise
• Reverse chatter

Cause:
Pressure regulator valve bore wear allows leakage and contributes to erratic pump slide movement.

Correction:
Repair the valve bore and restore pressure control to the system with this oversized pressure regulator valve and reamer kit.

A worn OE pressure regulator valve can be detected in two ways. The first is a dynamometer test that reveals low line pressure during boost conditions (look for 50-100 psi less than specified in Reverse). The second is vehicle symptoms such as clutch slippage, reverse chatter and 3-4 clutch failure. Any of the above problems indicate bore wear that should be addressed.
To address pressure regulator leakage in GM 4L60-E, 4L65-E and 4L70-E pump bodies, Sonnax offers oversized pressure regulator valve 77917-07. The Sonnax valve permits pump covers to be restored to OE specifications by correcting for wear and leakage at the pressure regulator valve.

• Refurbish the pump cover by reaming the bore and installing an oversized pressure regulator valve
• The pressure regulator valve helps restore control over the pressure regulating circuit by eliminating leakage

Note:
Boost valves should be checked for leakage at the same time the pressure regulator valve is being replaced.When oversizing the pressure regulator valve, it is recommended to move up one boost ratio.

SONNAX Installation Instructions