Accessory Drive

[dvd]

My A-4 has the minor rattling sound like bolts in a can. Could this sound be minimized by merely adding a new accessory drive?

[roadnsky]

My A-4 has the minor rattling sound like bolts in a can. Could this sound be minimized by merely adding a new accessory drive?

This from Don...


RATTLING or CLICKING sounds in the accessory drive:

"We believe these noises are caused by backlash and general looseness within the gear train between the small drive gear on the aft end of the crankshaft, the gear on the accessory drive, and the large idler gear (5” dia) which connects these two gears,
These gears are all rather “crude” with diagonal teeth (which appear to be forged). The idler gear itself has a brass bushing pressed into its center and it rotates on a steel spindle that is pressed into the aft end of the block.
This brass bushing is fed by the pressure oil system through a small hole in the spindle, and is loose enough (by design) to allow a generous amount of oil to flow out along the gear itself to be “flung” unto the accessory drive gear, providing an oil supply to that unit.
We have seen these bushings to have .003” to .004” on very low time engines.
It is important to note here that we have never seen or heard of any serious problems associated with these noises.
In years past, we have disassembled engines to investigate some of the more pronounced clicks and rattles, and have never successfully defined any measurable differences between engines that have the noises and those that do not"

As always IRMV, but you may not need to replace...

[67c&ccorv]

Propeller cavitation noise sounds a lot like marbles in a tin can.

[hanleyclifford]

If you have an accessory drive with a tachometer drive that is not being used, it could be the source of the "rattle".