Why Am I Hearing Gear Noises?

[zav6a]

When the battery is low inn particular. Try taking the belt off.

[Russ McCutcheon]

Went flying today and checked, I can hear my wine easily without the headset on.

[RV7ator]

Stethoscoped the engine today. The governor seems the source. The buzz/whirr/whine certainly emanates all along the body and most loudly from the housing aft end. Not so much around the engine. But this doesn't necessarily exonerate the driving accessory gear until the governor itself is checked out. It's a PCU5000 (aka Jihostroj).

It was put on a test stand prior to installation to assure proper performance. Prop shop gets a call Monday.

BUT! Oh, my goodness! #1 and #3 each have loud tappet noises, seemingly one each judging by the tempo. ASP still isn't out of the woods. Oil temp was 80F and CHTs were well into the 200s at shutdown after five minutes with up to 2000 rpm. Plenty of time to pump up lifters (and they shouldn't have been flat, anyway).

Aaarrgh!

John Siebold

[mahlon_r]

Some times what you think is tappet noise is really normal piston slap. If you take the rocker covers off and the valves have 0 lash, the lifters are pumped and it might have been piston slap you heard. Normal piston slap can be pretty loud, especially at idle speeds. If the governor is the whine, it is probably ok and not defective. They all seem to whine a bit some louder then others.
Good Luck and Happy New Year,
Mahlon

[RV7ator]

Thanks, Mahlon,

I'll dig deeper on the governor noise.

The valve train noise is only 1 and 3; 2 and 4 are quiet. Also, it's half the rpm. Piston slap would be the same as rpm, no? I'm going to have better educated ears listen.

John Siebold

[N616LM]

I also seem to have gear noise on cold oil. My engine is an IO-360 A1B6. Any more information on the source?

Thanks,
Jay Martin

[zilik]

A friend with a 10 had a gear noise on startup, but only on startup. Once it was warmed up it went away and did not happen till the next cold start. We checked everything but came up with nothing.

Then the first oil/filter change occurred and the noise went away. It was the filter!

[sblack]

what is piston slap?

[edsong]

The S2-B i fly makes the same noise. All the gears in the accessory case are straight cut gears. Ever notice in a manual transmission car the reverse gear whines? They are straight cut gears. The rest are helical cut gears like the ring and pinion. Designed that way to be quiet.
I'll bet thats what your hearing.

Eddy

[lr172]

Originally Posted by RV7ator

Also, it's half the rpm.
John Siebold

I am curious how you determined this. At 600 RPM, there are 10 revolution events per second. Can you really count that fast?

Further, I don't believe that piston slap will always occur on each stroke. Some times it will only slap on the power stroke (half the RPM). It really depends on what is causing it. I once had a noise at idle on a big block chevy. I was pretty sure it was valve train related. Sure enough, it was piston slap. In my case, the piston pin was tight in the piston bore, causing slap on each stroke. I was led to believe that slap caused by excessive clearance will only occur or be more noticeable on the power stroke.

Larry