Symptoms:

  • Delayed engagement
  • Gear ratio codes
  • Low pressure
  • High line pressure in Reverse
  • Repeated case breakage
  • TCC codes

Cause:

Wear at the pressure regulator bore, especially at the balance end, results in the PR valve not being able to stroke to the lower line pressure position. This results in high line pressure. Leakage of line to exhaust reduces line rise. Slow line rise in response to engine load eventually burns a clutch or reduces TCC apply pressure.

Correction:

Refurbish worn bores using the specially designed F series tool kit and the Sonnax VB-FIX and install the Sonnax oversized pressure regulator valve and boost valve assembly

Warning:

Reamer kit F-72754-TL3 is no longer in production but may be available from distributor inventory.

4T80-E

Oversized Pressure Regulator & Boost Valve Kit
Part No. 72754-03K

Fits '94-later units.


You need this if... View Instructions Find a Distributor

GM transmissions with a 4T80-E can experience delayed engagements, gear ratio codes, low/high line pressure, case breakage and TCC codes due to excess wear in the main pressure regulator valve bore. After reconditioning the bore, installing Sonnax oversized pressure regulator valve and boost valve kit 72754-03K will restore hydraulic integrity for proper line pressure control in all ranges.

  • Hardcoat anodized aluminum valves combat premature wear
  • New boost valve is calibrated to work with OS pressure regulator valve

Reamer kit F-72754-TL3 is no longer in production but may be available from distributor inventory.

  • Pressure Regulator Valve
  • Boost Valve
  • Boost Sleeve
  • Spring
  • 4T80-E Oversized Pressure Regulator & Boost Valve Kit 72754-03K
  • 4T80-E Oversized Pressure Regulator & Boost Valve Kit 72754-03K

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.

4T80-E Oversized Pressure Regulator & Boost Valve Kit Vacuum Test Locations