Low speed shudder. Drive shaft issue. One or more of the 3 rear u-joints is toast. Or your carrier bearing rubber isolator is torn and time to replace the carrier. Grab the drive shaft at the carrier. If you can move it more than about an 1/8" in any direction, your carrier is toast.
Carrier #3 for me in a 125k on my '05. Carrier #2 on my '07 in 72k.