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

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

Correction:

Install new Sonnax boost assembly to restore hydraulic integrity and prevent leakage.

4L60-E, 4L65-E

Boost Valve Kit

Part No.

77898E-4K

 Boost Valve Kit
  • 77898e-4k_combo

  •  Boost Valve Kit

Small_77898e-4k_combo Small_77898e-4k

4L60-E, 4L65-E

Boost Valve Kit

Part No. 77898E-4K

  • Valve .470", 1 Groove
  • Sleeve
  • O-Rings (2)

Replaces early pump design, 1.907” length (long) sleeve, large OE ratio assemblies.

Complaint:

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

Cause:

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


Correction:

Install new Sonnax boost assembly to restore hydraulic integrity and prevent leakage.

GM 4L60-E and 4L65-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-4K is a large OE ratio assembly that will restore hydraulic integrity and prevent leakage in units with early-design pumps. See chart below for usage details and other boost valve options.

EPC Spool Valve/Sleeve
Design
OE 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 V: 1 Groove 77898E-6K V: 1 Groove
Sleeve 1 Groove S: No Groove S: No Groove
.490"
Upgrade for OE .470"
Valve N/A 77898E-K V: No Groove 77898E-3K V: No Groove
Sleeve S: No Groove S: No Groove
Late Pump Design, 1.890" Length (Short) Sleeve
.421" Valve 3 Bands 77898E-14K V: 3 Grooves

No Sonnax ratio available.

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

No Sonnax ratio available.

Sleeve 1 Groove S: No Groove
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.

  • Patent No. 6,619,323

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