Some 2017-2019 Toyota Tacoma trucks equipped with the BD20 differential (non-TRD) may exhibit a noise or vibration at the rear of the vehicle at low speeds or while braking. This condition may be caused by excessive clearance between the brake drum and axle drum flange.
Inspect the rear drum and brake assembly for any signs of defects or wear. Also inspect the rear axle flange for corrosion/rust buildup. If found, repair/clean as needed. Road test before proceeding further.
Measure the dimeter of the axle flange boss using a digital or dial caliper. Take measurements in three locations around the flange to verify diameter. The specification is 108.000 mm – 107.946 mm (4.252 in. – 4.250 in.). If out of specification, replace the axle.