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6.6L Gas V8 (L8T)

The iron-block workhorse. Tech and reliability discussion for the 6.6L L8T V8 and the 6-speed / 10-speed heavy-duty transmissions.

254 topics in this forum

  1. New 2025 HD gas 300 miles needs VALVE BODY 1 2

    By dddavel,
    • 18 replies
    • 5.5k views

  2. So how many miles are we seeing out of the L8T/6L90 Powertrain?

    By UltimateToolReviews,
    • 2 replies
    • 1.5k views

  3. Torque converter

    By 22 6.6gasser,   
    • 4 replies
    • 1.9k views

  4. Transmission Fluid--Which to use?!?!?! 1 2

    By Truston Gunter,
    • 17 replies
    • 27.7k views

  5. "Allison" 10 speed hard upshift gears 7-8 1 2

    By UWSkier,
    • 28 replies
    • 11.5k views

  6. Correct way to service 2024 l8t allison trans? 1 2

    By Aimatdeer,
    • 22 replies
    • 6.3k views

  7. "Severe Service?" - 6 spd trans fluid change schedule for AT4 3500 HD carrying a 3000# camper practically full time

    By markny,
    • 9 replies
    • 1.6k views

  8. 2020 hd2500 cruise stopped working

    By Pythonhunter,
    • 2 replies
    • 508 views

  9. 2024 Silverado ZR2 2500 6.6L gas engine failure 1 2 3 4

    By Eric.V,
    • 49 replies
    • 46k views

  10. In depth dive into the Allison 10spd valve body issue.

    By No F-bdy Bs,
    • 1 reply
    • 1.4k views

  11. P0446 Evap System Code

    By Another JR,
    • 12 replies
    • 2.7k views

  12. Pulsar LT, anybody using one?

    By Sonders,
    • 8 replies
    • 3k views

  13. Why does a F350 Tremor Ride So Much Nicer Than My Silverado? 1 2

    By UWSkier,
    • 26 replies
    • 5.7k views

  14. Are the 6.6 l8t engines inherently noisy? 1 2 3 4

    By DuckBoi,
    • 48 replies
    • 21.8k views

  15. 6L90 Pan Drop Question

    By UltimateToolReviews,
    • 5 replies
    • 1.7k views

  16. 2024 chevy l8t with 10 speed allison temps

    By Aimatdeer,
    • 3 replies
    • 1.5k views

  17. Just drained 10 quarts of oil from my L8T 1 2 3

    By BuckWallace,
    • 30 replies
    • 6k views

  18. 6.6 gas dually specs needed

    By buelldude,
    • 11 replies
    • 2.9k views

  19. Rusty front axle on 2025 Silverado 2500 4WD. 1 2

    By superdave160,
    • 26 replies
    • 5.4k views

  20. Trying to do what the manual says 1 2

    By Gary Camille,
    • 29 replies
    • 6.6k views

  21. Cut open the oil filter on my 800mi L8T

    By No F-bdy Bs,
    • 0 replies
    • 1.1k views

  22. 2024 Silverado 2500 Gas Hairline Crack in Manifold

    By ChristopherF,
    • 7 replies
    • 2k views

  23. '24 2500HD Gasser Allison 10spd Valve Body Issue 1 2

    By silversteverado,
    • 23 replies
    • 8.4k views

  24. Which oil filter, not so simple! 1 2 3 4 14

    By Pryme,
    • 206 replies
    • 67.3k views

  25. I Installed the (6L90E) PML transmission pan - report

    By mrjulian416,
    • 5 replies
    • 4.9k views
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