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  • Broken parts due to excessive line pressure
  • Burnt clutches
  • Erratic line pressure
  • Harsh shifts
  • High line pressure
  • Restricted converter/lube flow
  • Soft shifts


Excess pressure regulator valve and sleeve wear allows fluid loss and/or causes valve hang-up, preventing normal line pressure control.


Restore appropriate line pressure in all ranges by reconditioning the bore and installing wear-resistant Sonnax oversized pressure regulator valve kit.

ZF8HP45, ZF8HP55, ZF8HP70

Oversized Pressure Regulator Valve Kit
Part No. 35740-01K

You need this if... View Instructions

Vehicles equipped with ZF8HP45, ZF8HP55 and ZF8HP70 transmissions often develop erratic or high line pressure due to excessive wear in the OE pressure regulator valve bore and/or sleeve. This wear allows critical oil loss, preventing proper line pressure regulation. Without correct balance oil pressure, the PR valve will be out of its desired position, resulting in line pressure instability and possibly restricting cooler and lube flow. A deteriorated bore can cause lowered line pressure, resulting in soft shifting and burnt clutches. Reconditioning the bore and installing Sonnax oversized pressure regulator valve kit 35740-01K renews pressure regulator action for revived line pressure control in all ranges.

  • Hardcoat anodized aluminum valve combats premature wear
  • Annular grooves help center valve in bore to reduce side-load wear
  • Valve
  • Sleeve

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

ZF8HP55 Valve Body Layout

Zf8hp55 vbl thumb

ZF8HP45, ZF8HP70 Valve Body Layout

Zf8hp45 70 vbl thumb

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  • 35740 01k combo
  • 35740 01k

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.

  • 35740 01k vacuum