I took the car in for service because the check engine light came on again. Car had gone haywire again in the snow when I had to floor the gas to maintain forward motion going up hill in snow. Complete new transmission required.
Engine shudder under load and low RPM. CarMax replaced transmission under their warranty. GMC warranty had expired. I don't think this was the root cause.
replace CV axle (driver's side)
Transmission module was replaced During trip for Trans module replacement, Extended warranty repair was made to the trans for the broken 35R clutch wave plate inside the transmission. Service tech preformed stating abnormal wear
3/5/R Wave Plate shattered. Had to rebuild transmission.
My gear shift was making a very loud noise and would not move smoothly when put into any gear. The symbols such as "R" for reverse and "P" for park would not light up. The gear shift was replaced but symbols still do not light up as they did when new