Axle Noise - Knock

Knock, which can occur on all driving phases, has several causes including damaged teeth or gearset.

Fig 1: Identifying Damaged Teeth Of Pinion And Ring Gear

Courtesy of MAZDA MOTORS CORP.

In most cases, one of the following conditions will occur:

1. A gear tooth damaged on the drive side is a common cause of the knock. This can usually be corrected by grinding the damaged area.
   Fig 2: Identifying Damaged Teeth Of Pinion And Ring Gear

   Courtesy of MAZDA MOTORS CORP.
   NOTE:

   • Measure the end play with a Dial Indicator with Bracketry and not by feel.
2. Knock is also caused by excessive end play in the axle shafts. Up to 0.762 mm (0.030 inch) is allowed in semi-float axles. The frequency of the knock will be less because the axle shaft speed is slower than the propeller shaft.