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Sonnax Performance Pack for GM 4L80-E/4L85-E Transmissions


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Performance Pack for GM 4L80-E/4L85-E Transmissions
1 left in stock
Performance Pack
  • GM 4L80-E/4L85-E Transmissions
  • Heavy-Duty Recalibration
  • Quick-Firm Shifts
  • Sold as a Kit
  • Free Shipping - Ships

    HP-4L80E-01 is rated 3.0 out of 5 by 1.
    Rated 3 out of 5 by from Great - except for the boost valve and sleeve Installed the HP-4L80E-01 boost valve and sleeve and a brand new Transtec pump and got vacuum readings of 12in-Hg for reverse and 16in-Hg for torque signal (pump halves separated and using a plexi plate). The Sonnax 4L80E vacuum test guide states that the torque signal circuit and reverse circuit both should hold minimum 18in-Hg of vacuum (0.035" calibration hole set to 5in-Hg and sealed/max set to 25in-Hg). Talked with tech support and it sounds like tolerance stack up. The boost valve sleeve ID was as large as allowed and the boost valve OD was as small and allowed. Sonnax said they tested one off the shelf in their shop and got readings of 15in-Hg and 20in-Hg (minimum required stated as 18in-Hg). I noticed Jakes Performance quit using the Sonnax boost valve in their kits and now recommends the stock GM boost valve and sleeve and with a different spring. Sonnax never said why they only got 15in-Hg, and never said if my vacuum readings would be acceptable. Lastly, I also asked why the instructions for dual feeding states to only remove the second sealing ring on the center support (normally I remove both the second sealing ring on the center support and the inner seal on the direct drum), but didn't get an answer for that either.
    Date published: 2022-11-21
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