• Uncontrolled pressure in Reverse
  • Soft shifts
  • Delayed Reverse
  • Low line rise
  • Throttle buzz
  • Erratic Reverse pressure
  • Clutch failure
  • Band failure
  • Damaged case


Wear at the pressure regulator valve bore and reverse boost sleeve allows valuable EPC, line pressure and reverse boost to exhaust.


The Sonnax kit includes an oversized pressure regulator valve to restore correct clearances for proper hydraulic control, and a replacement reverse boost valve assembly.


The oversized reverse boost valve and sleeve supplied in these kits must be used when replacing the PR valve.


Oversized Pressure Regulator & Boost Valve Kit
Part No. 76948-16K

Fits '95-earlier only.

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

Common complaints in vehicles with AODE and 4R70W transmissions is low line pressure resulting or band and/or clutch failure, or throttle-sensitive buzz, especially when hot. These issues can be caused by severe wear at the outboard pressure regulator valve spool or bore area. Wear at this location allows EPC oil to leak to exhaust, resulting in poor line rise. As oil temperature increases it becomes less viscous, an more leakage occurs. Wear at the inboard balance spool bore is also very common, which can result in excessively high lie pressure that can damage the case. The Sonnax oversized pressure regulator valve and matching boost valve kit 76948-16K restores valve-to-bore clearances so the pressure regulator valve can maintain correct pressures.

  • Improved PR/EPC reaction area ratio provides higher line rise response to EPC pressure, which results in noticeably firmer shifts.
  • Hard-coat anodized aluminum oversized pressure regulator valve resists wear.
  • Annular grooves added to oversized pressure regulator valve prevent side loading wear.

There are two reaming options available for this kit:

  • Reaming Option 1: Tool Kit F-76948-TL. This option includes reamer, reamer jig and guide. It requires reaming fixture VB-FIX but not bore sizing tool.
  • Reaming Option 2: Tool Kit 76948-TL4. This is a bench tool kit and does not require VB-FIX. After reaming with bench tool kit, use Bore Sizing Tool 76948-BST (sold separately) to provide exact sizing and improved bore finish.

Either tool kit works for all model years.

  • Pressure Regulator Valve
  • Reverse Boost Valve
  • Reverse Boost Sleeve
  • 4R70W, AODE Oversized Pressure Regulator & Boost Valve Kit 76948-16K
  • 4R70W, AODE Oversized Pressure Regulator & Boost Valve Kit 76948-16K
  • 4R70W, AODE Oversized Pressure Regulator & Boost Valve Kit 76948-16K details

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

4R70W, AODE Oversized Pressure Regulator & Boost Valve Kit Vacuum Test Locations