Cat 350L Grinding noise on swinging

[Mulla1]

Just need a little help as to where the problem might be on a Cat 350 Excavator. It swings OK but on stopping the swing there is a mild grinding / Growling noise. I noticed a very small bit of oil leaking from around the swing gear. I want to fix the problem before it becomes a big problem. I opened the inspection plate at the front of the swing gear between the boom mounts and there is about 3 inches of grease in the box and the ring gear looks in good shape. Any help would be appreciated as I have a parts manual but not a service manual. Thanks

 

[Nige]

There are a number of 350 models. Got a Serial Number to narrow it down a bit.?

Swing brake friction discs wearing out maybe.?
When you stop do you simply release the joystick, or do you counter-swing in the opposite direction and only release the joystick when the upper frame stops moving.?
What does the oil in the swing box look like.?

 

[Mulla1]

Thanks Nige, the serial No. is 9DK00120*.
When Stopping I just release pressure off the joystick and it stops ....except a light growl noise. when I took the inspection cover off the swing box I didnt see any oil in there only about 2 to 3 incehes of black grease. There are only very small drips of black oil coming from the underneath of the swing box and running down onto the top of the track frame.
Are the brake friction discs inside of the swivel motor or the swing motors ?

 

[Nige]

when I took the inspection cover off the swing box I didnt see any oil in there only about 2 to 3 incehes of black grease.

I wasn't talking about the swing pinion compartment. I was referring to the planetary assembly that connects the swing motor to the pinion. There are two of them and they have dipsticks to measure oil level. They also contain the swing brakes. See illustration.

 

[Nige]

When Stopping I just release pressure off the joystick and it stops ....except a light growl noise.

Try an experiment. At a reasonably low engine RPM and with the bucket fairly close to the machine start the upper frame swinging in one direction, doesn't matter which one. Once it gets up to speed move the joystick fully over in the opposite direction to which you are swinging. That's known as "counter slewing" and it won't do the machine any harm. As soon as the upper frame stops moving release the joystick to the centre. As the upper frame comes to a stop do you still hear the grinding/growling noise.?

 

[Mulla1]

The oil in the swing motors was clean and at the correct level.
I'll go down to the machine and do that test you suggested. I'll get back to you.

 

[Mulla1]

Nige did the swing test and I couldn't hear the growl but only the hydraulic "noise "as the direction of turn was reversed. The growl is more prominent when the stick is out and you swing either way and release pressure on the joystick to stop.

 

[Nige]

did the swing test and I couldn't hear the growl but only the hydraulic "noise "as the direction of turn was reversed.

Based on that and your described method of normal operation of just letting the joystick go to stop the machine I would say the noise is coming from the swing brakes, which are really only really there to hold the upper frame in position once it’s stopped. Counter-slewing is the way most operators run machines of the size of a 350 AFAIK. I may be wrong.

 

[Mobiltech]

Is the noise the same in both directions of swing.

I don’t think it would be a brake issue because the brakes are on a few seconds delay and only apply as a park brake after stopping.
Does your machine have a fine swing switch? If you switch it on the brakes should not apply at all.

I guess the brake discs could chatter if warped bad enough.
The brakes can be inspected by removing the top of the motor.

 

[Nige]

Does your machine have a fine swing switch? If you switch it on the brakes should not apply at all.

That would be the next test. The switch is on the left console.

 

[Mulla1]

Thanks for the replies. I tried it with the Fine Swing switch on and it didnt make any difference. As the machine is running in override mode both on the hydraulic pump and Engine Speed control would this switch be effective ? (The Cat mechanic was unable to resolve the loss of communication between the ECU and monitor so put it in override to continue operating. )
Even when slewing very slowly and say through 30 degrees there is still a very low noise which sounds like gear meshing.

 

[Mobiltech]

Is the sound fast or slow? Would be nice to hear it on a video.

 

[Mulla1]

The sound is slow and methodical in that is just sounds like big gears meshing. Not a real worrying noise but the fact that it hasnt been there before ! As said I checked the ring gear and it appears to be about 2 to 3 inches of grease in there and the oil levels in the two swing motors is correct. I'm away from the machine but will try to phone tape the noise when back up there.

 

[Lagwagon]

Sounds like you have a collapsed bearing in one of the planetary gears. I’d be dropping the oil from the slew hub into a clean container and get a spotlight on it looking for metal.

 

[Nige]

With the way the drains on the swing drives are set up (see photo in Post #4) it should be easy enough to drain a litre of oil out of each one to check for sparklies.

 

[Mulla1]

Yes the sound could be bearing noise. Thanks
I'll take a sample of oil and run a magnet through it.
I'll get back to you once Ive got a result.

 

[Hffhvg]

Has this problem been always present or recent? I don’t have a CAT but this is a page from operators manual of my 15ton excavator. I don’t know if this applies to heavier machines, but maybe it’s just the reduction unit of the slew motor, turning of the gears and friction? Or is it like a really apparent noise like something might brake any minute?
Maybe make a video of the noise while slewing?

 

[Mulla1]

Thanks Hffhvg interesting reading the page from your manual. Perhaps thats just it.....The noise itself is not a loud noise and nor does it sound like something is about to fail. It's just that it wasn't there two weeks ago. I have been working the machine a lot more, usually 10 hours per day and perhaps its just wear and tear. The machine swings smoothly and operates as it should except the low "gear" noise as it comes to a stop and during VERY slow slewing, both left and right. I'll be back at the machine in a few days time and I'll drain oil from both swing motors and check for metal.