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Symptoms:

  • 3-4 Clutch failure
  • Low line rise
  • Poor shift quality
  • 2-4 Band failure

Cause:

A worn boost sleeve can allow torque signal and reverse oil cross leakage or leakage to sump.

Correction:

Sonnax valve and sleeve kits restore hydraulic integrity and prevent leakage.

WARNING!

OE has made multiple pump design changes. Transmission will not function properly if the wrong length sleeve is installed. Verify length of OE sleeve and select Sonnax kit with equivalent sleeve length.

EPC Spool OE Valve/Sleeve Design Sonnax with O-Rings Sonnax “Factory Style”
Early Pump Design, 1.907" Long Sleeve
.421" Valve: 1 Band

No Sonnax ratio available.

Sonnax 77898E-4K may be used, but noticeably firmer shifts will occur.

No Sonnax ratio available.

Sonnax 77898E-6K may be used, but noticeably firmer shifts will occur.

Sleeve: No Groove
.470" Valve: 2 Bands 77898E-4K Valve: 1 Groove 77898E-6K Valve: 1 Groove
Sleeve: 1 Groove Sleeve: No Groove Sleeve: No Groove
.490"
Upgrade for OE .470"
Valve: N/A 77898E-K Valve: No Groove 77898E-3K Valve: No Groove
Sleeve: N/A Sleeve: No Groove Sleeve: No Groove
Late Pump Design, 1.809" Length (Short) Sleeve
.421" Valve: 3 Bands 77898E-14K Valve: 3 Grooves

No Sonnax ratio available.

Sleeve: No Groove Sleeve: No Groove
.472" Valve: 4 Bands 77898E-16K Valve: 4 Grooves

No Sonnax ratio available.

Sleeve: 1 Groove Sleeve: No Groove

4L60-E, 4L65-E, 4L70-E

Boost Valve Kit
Part No. 77898E-16K

Replaces late pump design, 1.809" length (short) sleeve, large OE ratio assemblies.

You need this if... View Instructions

GM 4L60-E, 4L65-E and 4L70-E transmissions frequently have poor line rise, which can result in 3-4 clutch, 2-4 band failure or poor shift quality. The duty cycle of the EPC solenoid causes the boost sleeve to wear quickly. Oil entering the torque signal orifice leaks past the boost valve and exhausts at the reverse orifice, resulting in poor line rise. Reverse oil can exhaust both to the sump and back through the torque signal orifice. The outside diameter of the boost sleeve also allows some leakage through the pump body, which decreases pressure rise.

Sonnax boost valve kit 77898E-16K is a large OE ratio assembly that will restore hydraulic integrity and prevent leakage in units with late-design pumps. See chart below for usage details and other boost valve options.

  • Valve 4 Grooves
  • Sleeve
  • O-Rings (3) 1 Extra
  • 77898e 16k combo
  • 77898e 16k
  • 77898e 16k oe measurement

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

  • 77898e 16k in test