Tool Required VB-FIX Required

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

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

Correction:

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

Tool Required VB-FIX Required

4R70W, AODE

Oversized Pressure Regulator & Boost Valve Kit

Part No.

76948-16K

Oversized Pressure Regulator & Boost Valve Kit
  • 76948-16k_combo

  • Oversized Pressure Regulator & Boost Valve Kit

  • 76948-16k_compare

Small_76948-16k_combo Small_76948-16k Small_76948-16k_compare

4R70W, AODE

Oversized Pressure Regulator & Boost Valve Kit

Part No. 76948-16K

  • Pressure Regulator Valve
  • Reverse Boost Valve
  • Reverse Boost Sleeve

Fits '95-earlier only.

Complaint:

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

Cause:

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


Correction:

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

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.
WARNING:

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

NOTE:

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.

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

  • Test Locations

Click here to view PDF if instructions do not appear below.

It appears you don't have a PDF plugin for this browser. Click here to view the PDF file.

Related Tech Articles

Contact a Sonnax Distributor to purchase this part.