• Poor shift quality
  • Burnt clutches
  • Flare shifts
  • Soft shifts
  • Clutch slippage
  • Low line pressure
  • Ratio codes


Loss of oil pressure due to worn components in critical oil circuits.


Zip Kit seals critical pressure losses. Drop-in parts install quickly and easily.

8L45, 8L90

Shift Zip Kit®
Part No. 8L45-8L90-SHIFT-ZIP

For shift-related complaints.

View Instructions Find a Distributor

Sonnax shift Zip Kit 8L45-8L90-SHIFT-ZIP targets the root cause of mulitple shift-related complaints by sealing the critical circuit pressure losses in the GM 8L45 and 8L90 valve body. The kit contains uniquely designed parts to prevent the loss of pressures within the signal accumulator, clutch control and 1-3-5-6-7 accumulator piston circuits. These solutions target wear that results in multiple shift quality complaints and burnt clutches. No special tools are required for installing these parts.

The Zip Kit quick guide provides clear and easy instructions on one sheet to get the unit sealed up and back on the road fast. In addition to general rebuilding tips and technical information, the techncial booklet included in this kit contains vacuum testing information and locations at other key areas of the valve body.

  • Drop-in Zip Valve parts install quickly and easily, no reaming or special tools required
  • Uniquely designed parts address root causes of shift complaints by sealing critical pressure circuits
  • Detailed technical booklet included with in-depth rebuild and inspection tips for comprehensive valve body repair
Learn More About Zip Valve™ Drop-In Repairs
  • S1/S5 Clutch Control Valve Kit Fits 1 of 2 locations
  • S2/S3/S4/TCC Clutch Control Valve Kit Fits 1 of 4 locations
  • 1-3-5-6-7 Accumulator Piston Kit
  • Signal Accumulator Pistons, Sleeves, Springs, End Plugs & O-Rings (7)

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.

GM 8L45, 8L90 Valve Body Layout

GM 8L45, 8L90 Valve Body Layout
  • 8L45, 8L90 Shift Zip Kit® 8L45-8L90-SHIFT-ZIP
Sonnax Zip Kit

The Sonnax ZIP KIT®

The First Step in Correcting Common Shift Problems

It's easy to restore and extend vehicle shift quality with Zip Kits. Uniquely designed, drop-in Sonnax parts target the root cause of valve body complaints and stop critical circuit pressure losses in the most common problem areas of the transmission.

Learn More About Sonnax Zip Kits