Rotax 912 ULS Gearbox

I am starting to hear what sounds like a metallic screeching sound when the engine is at low RMS (1800-2500). It is not a constant sound, it comes and goes every couple of seconds. It's hard to tell where it's coming from but when I pull the prop through it makes a screech (kind of metallic) sound every once in awhile. The engine has 400 hours on it since new.

Before I send the gearbox in I though I'd ask if anyone else has had this happen.

Thanks
Gary

I'd recommend removing the top cowl, then having someone pull the prop through slowly while you pinpoint the sound you're hearing. It could be toward the back also, where the alternator is located.

Hey Gary - -

Can you post a link to a youtube video with audio so we can hear it ourselves ?

My guess is a bearing is not happy, and I (too) would not rule out another source like an alternator bearing.

One tool that has helped me locate the origin of sounds like this is a solid shaft stethoscope. You can get them from harbor freight or Amazon, they are not expensive.

Good luck, and let us know what you end up learning is the cause.

Charlie

I had a gearbox vibration with the 912ULS. It was in a Rans S-20 Raven I built in 2016. I noticed it initially when I was at the top of climb when I reduced the power from full throttle. The vibration started at 5500 and ceased by 4500 RPM. I also experienced a slight buzz in the rudder pedals and the floor. I replaced the gearbox and problem was solved.Your symptoms seems different.

Good luck in your troubleshooting,

Jim

Most likely overload clutch in gearbox. Check torque spec buy applying force on propellor with spring scale per Van's instructions...

Are you using AeroShell Oil Sport Plus 4?