Transmission Problems

A normal transmission makes an even noise like a, well – a normal landing gear transmission noise; how else would you describe such a unique sound? Listen to the audio of a cycle procedure. The purpose here is to demonstrate there are no abnormal noises.

This next lengthy audio [load time may be > 1 minute unless you have a really fast system and high-speed internet connection] demonstrates a retraction and extension procedure. It’s purpose is manifold.

1. You can hear the changing sound at the end of the retraction cycle when the main gear legs contact the gear bumpers snuggly.
2. The video also shows an ammeter in the system, while the voice is reporting the voltage.

Worn actuator screw [aka jack screw] and nut. If there are pits in the grooves of either component this will make a noise sounding like a rock crusher, a garbage disposal, or a thrashing machine depending on what area of the country you are from. See the 100-hour lubrication requirement; failure to perform this can lead to failure of the actuator screw and nut. Here is a photo of a pitted actuator screw; this will be very expensive to have repaired. A possible cause – Balls that are severely worn or damaged? Again, probably lack of adherence to the service recommendations.

Worn gear; the mating gear is not too pretty either. This condition may not be detectable except during the 500-hour or annual inspection and lubrication requirements specified in the Service Manuals. The gears in these photos are from a Dukes transmission that had no reported abnormal noises.

End play in the actuator screw where it enters the transmission housing casting. This video also shows the early style brake assembly which should be replaced with the later “plunger” style brake coil. See “brake coil” assembly.

There is a Checking Procedure in the Service Manuals for this loose bearing; also see the “Various Videos” section where you will find 3 videos of this condition. This is partially due to the weak design of the Dura type transmission. The offending bearing is swaged into the casting; Piper added a bearing retainer to prevent catastrophic failure after serial number 24-735, and provided a kit to retrofit serial numbers 1-735. This bearing being pulled out of the casting can be aggravated by excess friction in the push / pull cables [conduits] and improper down-lock micro switch adjustments – too close to the end of travel. Read this switch adjustment procedure, it’s better than the vague SM description. Piper also issued a SL-315 covering this transmission problem. This Piper publication is several pages long, covers quite a breadth of issues, unfortunately however contains errors. I’m working on a corrected version but it isn’t top priority. I’ll post it when available.

The Dukes type transmission is a more durable [sic] unit not suffering from this loose-bearing syndrome.

Resetting the landing gear transmission after a manual extension procedure – A really easy method and explanation.