Some 2015-2021 Transit vehicles equipped with rear wheel drive (RWD), single rear wheel only, and a U-joint at the transmission flange and rear driveshaft may experience a boom/hum/moan noise or vibration from the rear while driving. This noise or vibration is most prevalent at highway speeds: 112-121 km/h (70-75 mph) for 4.10 axle ratio, 121-128 km/h (75-80 mph) for 3.73 axle ratio, 136-145 km/h (85-90 mph) for 3.31 axle ratio. The noise or vibration may also be present to a lesser degree at roughly half of those speeds. This may be due to a 2nd order driveline frequency transmitted through the rear driveshaft, rear axle and into the body through the leaf springs. To correct the condition, follow the Service Procedure to install a driveshaft torsional damper.
