8HP55A, 8HP55AH, 8HP55A HIS

Tool Required

Symptoms:

• Poor line pressure control
• Low line rise in Drive
• Soft shifts
• Burnt clutches
• Premature clutch failure
• Low pressure

Cause:
Wear between the reducing valve and sleeve allows line pressure fluid, acting as cutback pressure, to exhaust to the sump. Wear between the pressure regulator valve and bore allows line pressure fluid to exhaust to sump. This combination of wear prevents proper hydraulic control of the pressure regulator valve and can cause high/low and erratic line pressure.

Correction:
Restore proper hydraulic control and renew line pressure performance by reconditioning the bore and installing Sonnax oversized pressure regulator valve kit.

Vehicles with ZF8HP50, ZF8HP75 and ZF8HP95 transmissions may exhibit insufficient line rise in drive ranges, soft shifts and/or burnt clutches. These problems may be caused by continuous oscillation of the reducing valve in the sleeve, creating excessive wear and a path for critical line pressure fluid to exhaust to sump. Reconditioning the bore and installing this Sonnax oversized pressure regulator valve kit restores proper hydraulic control and prevents wear by utilizing upgraded materials and minimal clearances.

• Sleeve is manufactured from highly wear-resistant billet aluminum to prevent future wear
• Hardcoat anodized aluminum valves combat premature wear
• O-Ringed sleeve provides positive seal to prevent critical line pressure fluid from leaking to exhaust
• Annular grooves help center the pressure regulator valve in the bore to reduce future side-load wear

Contains:

• Pressure Regulator Valve
• Reducing Valve
• Sleeve
• Spring
• O-Rings (2) 1 Extra

121785K Instruction Sheet