Hello,
I have a 2017, 2WD Tahoe with 63k miles. Was told by dealer I have a bad torque converter and need whole transmission replaced. Issue is sporadic and only happens going into first gear. Gears 2-6 shift fine. It sometimes takes a couple of seconds for first gear to engage. Checked transmission fluid at 174 degrees and fluid level about a 1/4 higher on dipstick at hot level. Fluid is clean. Was told no issue of fluid shows slightly higher. Any thoughts or suggestions of it could be anything else causing this ?? Thank you.

 

If that model has one I would drop the pan(or have the dealer do it) and change the filter and check that magnet in the pan. I am not a fan of flushes. My newest vehicle is a 2007 Tahoe. A filter and 4 quarts of oil is is not that much. Have you had that Tahoe since new?