Vehicles with GM 200-4R and 4L60 transmissions often have problems with poor Reverse boost or upshifts in manual low. These are generally caused by a worn Reverse boost valve sleeve or wear at the pump body. Sonnax offers a larger ratio (.283") Reverse boost valve kit K77898 to restore the hydraulic integrity of the assembly.
Due to the differences in the thermal expansion rate of steel and aluminum when the transmission approaches operating temperature, the sleeve has been allowed excessive clearance and scrubs the bore.

Sleeve O-rings seal the Reverse boost circuit and prevent leakage from the pump body bore
Sleeve and valve are made from hardened steel for increased wear resistance
Sleeve lands have been lengthened to add better sealing and stabilizing capabilities to prevent bore wear
Reverse boost valve spool lands have been lengthened to aid in maintaining hydraulic integrity
Drop-in Zip Valve™ parts install quickly and easily

Learn More About Zip Valve™ Drop-In Repairs

More From This Category

MANLEY Valve, Race Master, Intake, Bead Loc, 44.5mm Head Dia, 0.275 in. Stem Dia, 4.705 Length, For Ford, Each

MANLEY Valve, Race Master, Intake, Bead Loc, 44.5mm Head Dia, 0.275 in. Stem Dia, 4.705 Length, For Ford, Each

$51.07

MANLEY Valve, Titanium, Intake, Bead Loc, 2.25 in. Head Dia, 0.3415 in. Stem Dia, 5.35 in. Length, Each

MANLEY Valve, Titanium, Intake, Bead Loc, 2.25 in. Head Dia, 0.3415 in. Stem Dia, 5.35 in. Length, Each

$325.41

MILODON Valves, Exhaust, Race, Stainless Steel, 1.77 in. Dia, For Pontiac, 1968-70, 326, 350, 389, 400, 421, 455, Set of 8

MILODON Valves, Exhaust, Race, Stainless Steel, 1.77 in. Dia, For Pontiac, 1968-70, 326, 350, 389, 400, 421, 455, Set of 8

$475.89

AFR Exhaust Valve, Ferrea Titanium Valve, 1.880 + .100 w/Tip Race Exhaust, Set

AFR Exhaust Valve, Ferrea Titanium Valve, 1.880 + .100 w/Tip Race Exhaust, Set

$3,942.80

MANLEY Valve, Custom, Titanium, .3415 in. Stem Dia, Set of 8

MANLEY Valve, Custom, Titanium, .3415 in. Stem Dia, Set of 8

$2,804.20

MANLEY Valve, Race Flo, Intake, 2.08 in. Head Dia, 0.3125 in. Stem Dia, 5.176 in. Length, For Chrysler HEMI, Set of 8

MANLEY Valve, Race Flo, Intake, 2.08 in. Head Dia, 0.3125 in. Stem Dia, 5.176 in. Length, For Chrysler HEMI, Set of 8

$1,138.39