6.6L Gas V8 (L8T)

254 topics in this forum

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

   By silversteverado, August 18, 2024
   • 23 replies
   • 8.3k views
   • 
   • Chevyfan3
   • February 25, 2025

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

   By UWSkier, June 25, 2024
   • 28 replies
   • 11.4k views
   • 
   • UWSkier
   • July 1, 2025

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

   By markny, May 7, 2025
   • 9 replies
   • 1.6k views
   • 
   • lineman1234
   • June 20, 2025

4. 10 Speed Allison vs 6 Speed MPG 1 2

   By mtbadbob, November 14, 2023
   • 16 replies
   • 18.6k views
   • 
   • MORSNO
   • November 19, 2023

5. 10L1000 anyone with High Mileage ? I hate Damocles.... 1 2 3 4 5

   By Homer1959, October 29, 2025
   • 66 replies
   • 6.5k views
   • 
   • asilverblazer
   • February 5

6. 1st oil change at home

   By SkidooSteve12, September 4, 2020   

   • 2500HD
   • 6.6L Gas
   • (and 1 more)

     Tagged with:

     • 2500HD
     • 6.6L Gas
     • PF63E oil filter
   • 11 replies
   • 42.5k views
   • 
   • SkidooSteve12
   • September 18, 2020

7. 2020 2500 transmission slipping

   By Blac, November 30, 2020
   • 9 replies
   • 10.6k views
   • 
   • ug87
   • September 24, 2021

8. 2020 2500Hd feels like it is surging when towing a hill 1 2

   By Addison Reeder IV, November 14, 2020
   • 22 replies
   • 17.5k views
   • 
   • zmania99
   • October 27, 2024

9. 2020 and 2021 2500s

   By Flash23, January 13, 2021
   • 6 replies
   • 2.8k views
   • 
   • MTU Alum
   • January 18, 2021

10. 2020 chev silverado 2500 hd growling noise during acceleration from somewhere in front 1 2

    By Bruce proko, January 19, 2024
    • 15 replies
    • 7.9k views
    • 
    • Bsggsb
    • December 1, 2024

11. 2020 GMC 2500 6.6 GASSER leveled with 35's MPG????

    By Gabe Bunn, October 1, 2020
    • 11 replies
    • 18.5k views
    • 
    • Ryan Morgan
    • May 19, 2021

12. 2020 GMC 2500 HD--Wheels and Tires--OPINIONS WANTED

    By Swafford09, September 28, 2021
    • 5 replies
    • 3.6k views
    • 
    • Kjduvall
    • January 10, 2022

13. 2020 GMC Sierra

    By Lenny Bonin 1, May 19, 2020
    • 1 reply
    • 1.6k views
    • 
    • Lenny Bonin 1
    • June 1, 2020

14. 2020 hd2500 cruise stopped working

    By Pythonhunter, June 3, 2025
    • 2 replies
    • 504 views
    • 
    • GMCustomerService
    • June 5, 2025

15. 2020 L8T 2500 Transmission Temperature Reaches 230 while towing

    By allycat75, September 8, 2024
    • 4 replies
    • 2.1k views
    • 
    • Another JR
    • September 9, 2024

16. 2020 Silverado 2500 HD

    By Trey249, October 20, 2023
    • 0 replies
    • 1.4k views
    • 
    • Trey249
    • October 20, 2023

17. 2020 Silverado 2500 Lt 6.6 Gas lifter problems

    By Jesus Aguirre, June 13, 2021
    • 1 reply
    • 6.4k views
    • 
    • Ray Pickle
    • June 17, 2021

18. 2021 2500 HD downshift clunk

    By SteveSr, May 20, 2021
    • 8 replies
    • 10.7k views
    • 
    • MacLaren
    • July 7, 2023

19. 2021 6.6 gas Hollow tapping noise

    By Dusilligaf, March 23
    • 10 replies
    • 641 views
    • 
    • AT4X Steve
    • April 21

20. 2021 Chevy Silverado 2500 HD L8T SELF DESTRUCT

    By Tallman3, April 1
    • 6 replies
    • 873 views
    • 
    • GMCustomerService
    • April 2

21. 2021 Silverado 2500 HD review

    By MacLaren, July 8, 2023
    • 0 replies
    • 3.4k views
    • 
    • MacLaren
    • July 8, 2023

22. 2022 3500HD Service 4WD and Parking Brake setting when shifting to park

    By nocturnalmotors, December 22, 2022
    • 4 replies
    • 3.1k views
    • 
    • nocturnalmotors
    • December 27, 2022

23. 2022 gas deliveries HD from Canada

    By Richard Meyers, July 16, 2022
    • 1 reply
    • 1.3k views
    • 
    • waltman
    • July 16, 2022

24. 2022 L8T 6.6 Oil Use Calculation (when to worry and when not to)

    By UltimateToolReviews, December 5, 2025
    • 6 replies
    • 975 views
    • 
    • UltimateToolReviews
    • December 6, 2025

25. 2022 Release

    By CaptainMorganNC, March 23, 2021
    • 8 replies
    • 9k views
    • 
    • SnowsledBen
    • April 5, 2021