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 (gas) and Allison 2000 (diesel) 6-speed automatic transmissions used in Sierra 2500HD/3500HD are 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). The Allison's proprietary Transynd fluid is critical — using non-approved fluid is the leading cause of premature solenoid wear. TCM software updates from GM address most calibration-related shift complaints.

The Allison 1000 and 2000 series automatic transmissions paired with Duramax engines in the Sierra 3500HD exhibit 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. GM and Allison have acknowledged this issue through multiple fluid specification updates and TSB 07-07-30-022.

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 service bulletins addressing cooler line seepage/connection concerns on full-size trucks/SUVs using these transmissions.

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 25-50 mph. The shudder mimics driving over rumble strips. GM issued multiple TSBs (18-NA-355, 19-NA-193) and eventually reformulated the transmission fluid specification. The root cause is the TCC friction material interaction with the original Dexron HP fluid formulation.

Same 4L60E transmission issues as Chevrolet C/K. Sun shell failure, 3-4 clutch pack burnup, and worn input drum.

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.

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 is a 1500-specific chapter - it is not the 4L80E story and should not be read across to the 2500/3500.