Info - Diagnostic Recommendations/Instructions for Rear Axle Gear Whine and/or Bearing Growl Noise

Some of the above vehicles may exhibit a rear axle gear whine and/or bearing growl noise during drive and possibly coast conditions. This noise may increase with higher speeds. This condition usually begins at 480 to 800 km (300 to 500 miles) and may worsen with additional miles.

The following diagnostic recommendations/instructions may be helpful if the vehicle exhibits the above condition:

1. Remove the axle cover pan and inspect for black, discolored fluid. The fluid may show sand particles.
2. Closely inspect the inner diameter of the ring gear for clumps of a black sandy residue. This residue is lapping compound that was not sufficiently cleaned from the axle during the manufacturing process.

If these conditions are found, the complete axle assembly should be replaced because all moving parts of the axle will be affected by the lapping compound residue.

Important: The lapping compound issue will not be present on vehicles built after August 10, 2005. Rear axle noise conditions on vehicles built after this date should be diagnosed and repaired using procedures found in SI.

If rear axle replacement is necessary, use the applicable part number below or any P/N that these supersede to. The Broadcast Code, HL1 or HL2 for example, can be found in VIS under Vehicle Component.

Starting with the Broadcast Code JN2 and JN3, there was a change made to the brake pipe attaching hardware. The attaching bolts for the brake pipes on the previous axles used 6.0 mm bolts and the current replacement axle assemblies require the use of 8.0 mm attaching bolts. Vehicles built with previous broadcast codes (i.e. FD3, HL1, HU5, EX5, FD4, HL2, HU6) will have had a 6.0 mm nut welded to the axle housing bracket. Replacement axles will have an 8.0 mm nut welded to the axle housing bracket.

The original brake pipes can be reused by utilizing a longer 6.0 mm bolt, washer and nut arrangement obtained locally. Place the longer 6.0 mm bolt through the welded 8.0 mm nut and use the 6.0 mm nut and washer on the back side.