Question 1

Torque converter shudder on the 8-speed automatic (Sierra 1500 T1)

Accepted Answer

Trucks with the 8L90/8L45 8-speed automatic can shudder or feel like driving over rumble strips at 25-80 mph, caused by moisture in the transmission fluid affecting the torque converter clutch. GM fixes it with a double/triple flush using updated Mobil 1 LV ATF HP fluid.

Question 2

Active Fuel Management lifter failure (5.3 V8)

Accepted Answer

GM cylinder deactivation (AFM, later DFM) uses collapsible lifters that can stick or collapse, causing a ticking noise, misfire, a check engine light (P0300 series) and possibly a bent pushrod or damaged camshaft. Common on 2007-2013 5.3 V8s and again on 2019-2022 5.3 V8s.

GMC Sierra 1500Sierra 1500 T1

Known issues and common problems

GMC Sierra 1500Sierra 1500 T1

Known issues and common problems

Torque converter shudder on the 8-speed automatic (Sierra 1500 T1)at 80000 km · 1 solutionsMedium

Active Fuel Management lifter failure (5.3 V8)at 160000 km · 1 solutionsHigh