In the past hour, my 2015 Silverado 1500 with a 6L80 transmission has started clunking when shifting from drive to reverse and vice versa. I’ve checked the u-joints and the rear differential, and it’s neither of those. It seems to be something inside the transfer case or the transmission. Has anyone experienced this, and if so, what was it?
It might be a loose transmission mount; that can cause everything to buckle. Do you put it in drive while still reversing or the other way around?
Bad engine mounts are pretty common in those models. It’s also normal for the drivetrain to get a little clunky as the truck ages.
Check the fluid levels in your transmission and transfer case. Low fluid can cause shifting issues and noises.
If you haven’t done so already, inspect the driveshaft for any play or damage. That could also lead to clunking sounds.
You may want to have a professional check it out, especially if it’s coming from the transmission. It could lead to bigger issues if not addressed.