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  • Bent valves
  • Low line rise
  • Delayed engagement
  • Gear loss


Extensive manual valve length, narrow OE spools and minimal valve support result in bore wear and bent valve.


Restore normal operation by installing upgraded Sonnax manual valve.

4L80-E, 4L85-E

Manual Valve
Part No. 34994-16

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. Installing improved Sonnax manual valve 34994-16 eliminates these problems and renews manual circuit pressure control.

  • Lengthened spools operate in non-worn portion of bore for added stability and wear prevention
  • Stem diameter increased over OE
  • Hardcoat anodized aluminum valve combats premature wear
  • Annular groove added to inboard spool to reduce side-loading

February 21, 2013

GM 4L80-E Vacuum Test Guide

Topics: Vacuum Testing Vacuum Test Guides Transmission GM 4L80-E Transmission

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  • 34994 16
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