Squelching noise when free spinning, post shim

Morning all!

Just installed RA Low pro bushes into my MK H92 box and ive shimmed up some shs 13:1 gears.

Now it’s sweet, I’m pretty happy with how the gears are shimmed up. Roughly 0.1mm play with each gear and they are happy to spin but if you spin them too fast they or one of them atleast, makes a high pitch squeal?

It’s quite strange almost like the gear is trying to spin so fast that its vibrating in the bush?

Ive tried adding an each shim to each gear but it only makes it too tight or doesnt really take the noise away?

Can’t attach a video for some reason sorry.

I think it might be the spur gear.
No grease on the gears at the moment and wont be able to put anything on them until tonight unfortunately.

Let me know your theories?


Just uploaded a vid to YouTube.

That is completely normal, as you said it’s just chattering in the bush, once you grease them all will be good :+1:


Sweet mate, cheers for the feedback.

Just the first time I’ve come across it after three or four gearboxes Ive shimmed. :joy::man_shrugging:

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Bushes need quite a bit of play to operate correctly and a hard shaft in a hard bush thats dry tends to catch and release setting up a harmonic vibration.
Put a drop of oil on each bush and it should stop


Yeah sweet, I’ve tried to leave a bit of play in there.

I’m out at work on nightshift and don’t get home until next wednesday. It’s killing me i just want to finish the build.:joy:

No I mean play on the shaft to bush fit not up and down play, you want to achieve the least amount of play possible with shims but still have enough that there is no tightness on rotation