P0741 on GMC: How to Diagnose & Fix

The 8L90 8-speed and 10L80/10L90 10-speed automatic transmissions experience shuddering during light throttle acceleration, particularly at highway speeds between 35-60 mph. The issue is caused by the torque converter lock-up clutch slipping and chattering. Harsh shifts between gears, especially 1st to 2nd and 2nd to 1st, are also commonly reported.

The Allison 1000 6-speed automatic transmission used behind the Duramax diesel in Sierra 2500HD/3500HD is widely regarded as extremely durable, but the Transmission Control Module (TCM) and solenoid pack do develop faults. Common issues include harsh 1-2 shifts, transmission sticking in one gear, slip codes, and the truck going into limp mode (3rd gear only). Using the wrong fluid or skipping fluid service is a common cause of premature solenoid wear. TCM software updates from GM address most calibration-related shift complaints.

The Allison 1000 automatic transmission paired with Duramax engines in the Sierra 3500HD exhibits torque converter clutch shudder during light throttle cruising between 40–65 MPH as the TCC applies and releases. This is caused by degraded transmission fluid, worn TCC friction material, or contamination in the hydraulic circuit.

GMT900 and early K2XX Yukon XL models with 6L80/6L90 transmissions commonly develop leaks at the transmission cooler line crimps or quick-connect fittings. Owners report red fluid spots, low transmission fluid, and in severe cases slipping or overheating if fluid loss is significant. This issue is widely documented in owner reports, and GM safety recall 14V-152 (GM bulletin 14121) covered 2015 Yukon XL models with the 6-speed automatic whose cooler line may not be fully seated in its fitting.

The 8-speed (8L90) and 10-speed (10L80) automatic transmissions in the Yukon XL develop a torque converter clutch (TCC) shudder felt as a vibration or shake at light throttle between 25-80 mph. The shudder mimics driving over rumble strips. GM issued TSB 18-NA-355 (covering 2015-2017 Yukon models with the 8L90) and changed to a reformulated Mobil 1 Synthetic LV ATF HP fluid. GM attributes the shudder to moisture absorbed by the original, hygroscopic fluid.

When the Savana 2500/3500 moved to the 6L90 six-speed for 2010, a new failure appeared that the old 4L80E did not have. GM's own service information for 2010-2014 Express and Savana vans with the 6.0L flex-fuel V8 and 6L90 acknowledges that torque converter clutch friction material wears faster than expected under high duty cycle use - towing, loaded cutaway bodies, sustained grades - and that the wear produces a driveline vibration or shudder. Owners feel it as a light-throttle judder at 40-60 mph, like driving over rumble strips, worst when the converter is in its slip-controlled lock range. The shed friction material then contaminates the fluid and works its way into the valve body and pump, which is how a shudder becomes a rebuild.

The light-duty Savana 1500 uses the 4L60E (later 4L65E) four-speed, not the heavy-duty 4L80E fitted to 2500/3500 models, and it is the weak link of the lineup. In van duty the converter clutch and overdrive cycle constantly at city speeds, and the 3-4 clutch pack and its apply seals cook. Owners describe a van that drives normally for a few miles and then flares between 3rd and 4th, or revs like it is in neutral once hot. Forum reports on 1996-2002 5.0L/5.7L and 2003-2014 5.3L 1500 vans repeat the same pattern; a plugged filter and burned fluid are usually found at teardown. This issue applies to the 1500 only; 2500/3500 vans use the 4L80E.

The heavy-duty 4L80E (4L85E behind the 8.1L and the diesel) fitted to Savana 2500 and 3500 vans develops a distinct failure set from the 1500's 4L60E. Owners report shuddering around 45 mph as the torque converter clutch tries to lock, hard or late shifts, no downshift on throttle demand, and in advanced cases the van reaching operating temperature and then behaving as though it is in neutral in every gear. Root causes documented on 3500 vans include a failed TCC PWM solenoid or its electrical circuit, worn valve body bores, and pressure loss from a worn pump. Commercial-fleet duty cycles - constant loaded stop-and-go, cutaway upfit weight at the top of the GVWR - accelerate all of it.

The 4L60E four-speed automatic in these trucks commonly fails in two ways. The first is a burnt 3-4 clutch pack. Transmission parts maker Sonnax traces most 3-4 slipping to low line pressure or to leaks in the third-gear oil circuit. Those leaks can come from input shaft seals, a leaking input drum, a clogged input housing checkball, a worn pump, a leaking 3rd accumulator checkball, worn accumulator pins, or worn valve body bores. The weak factory 3-4 backing plate also flexes when it applies, which builds heat. Heat can warp the 3-4 piston's rubber seal so oil pressure blows past it, and the clutches then slip and burn, so the truck slips in 3rd and 4th gear. The second failure is the sun (drive) shell. It can split in two, or the input gear can wear its internal splines smooth. Owners then report trouble shifting from 1st to 2nd or into reverse or overdrive, along with slipping and grinding noises.