My 2011 GMC Sierra makes a shudder type feel/noise when shifting in lower gears

Hi, your torque converter doesn't really play a part in any way until you get between 25-40 miles per hour, give or take. That also depends on load of acceleration at the time of engagement command. If you feeling the shudder in the area of those speeds, indeed it could be related to torque converter clutch slippage. This can be simply due to broken down fluid. I'd recommend - if this is the case - to replace all the transmission fluid you can - and even doo it twice if you can only get several quarts out at a time. Once refilled with the correct grade of fluid, drive the vehicle and see if it makes any difference. It may or may not. This is all a guess; a shudder can also be coming from engine misfires that feels like a transmission related issue due to the speeds it happens and the load the engine is under when it happens. As a result, it's too hard to tell. Seek guidance at a local shop near you. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.