• Bent valves
  • Low line rise
  • Delayed engagement
  • Gear loss
  • Broken AFL filters
  • Leaking AFL end plug
  • 2nd Gear starts
  • Code 68, 85, 86, 87
  • No upshifts


Extensive manual valve length, narrow OE spools and minimal valve support result in bore wear and bent valve. Leaking or damaged AFL filter or end plug causes driveability troubles.


Renew AFL operation and restore shift control by installing Sonnax drop-in AFL filter end plug and O-ring kit.

4L80-E, 4L85-E

Manual Valve Kit
Part No. 34994-16K

View Instructions Find a Distributor

The OE manual valve in GM 4L80-E and 4L85-E transmissions is prone to bending due to its length and relatively narrow spools. Once bent, the valve causes excess bore wear, allowing critical fluid to escape the chosen circuits. This can result in delayed engagement, low line rise and loss of gear.

It is also common for the AFL filter and its end plug to leak, resulting in 2nd Gear starts, no upshifts and various trouble codes. Installing improved Sonnax manual valve kit 34994-16K eliminates all these problems and renews AFL and manual circuit pressure control.

  • Lengthened spools operate in non-worn portion of bore for added stability and wear prevention
  • Stem diameter increased over OE
  • O-Ringed end plug positively seals bore to prevent leakage
  • Hardcoat anodized aluminum valve combats premature wear
  • Annular groove added to inboard spool to reduce side-loading
  • Drop-in Zip Valve parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • Valve
  • AFL Filter End Plug
  • End Plug O-Ring
  • AFL Filter O-Ring

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 4L80-E, 4L85-E, 400 Valve Body Layout

GM 4L80-E, 4L85-E, 400 Valve Body Layout
  • 4L80-E, 4L85-E Manual Valve Kit 34994-16K
  • 4L80-E, 4L85-E Manual Valve Kit 34994-16K