Gear train

[Magard]

I have a noise in the front of my engine. It’s been there for close to 30000 miles. It’s maybe a little worse. So I decided to try and do some preliminary looking around. I took the plug out where you bar the engine over in front of compressor. I have alittle backlash in the compressor drive gear. On quickserve it looks like the spring loaded gear should be taking out this slack. The noise is kinda tiny sounding. I’m wondering if I’m hearing springs making noise in this gear train. I have cut apart my oil filter last two oil changes and haven’t seen any at all. Just wondering how serious is it if the springs in gear train are loose and how common is this. Also the idler gear was put back in at .010 and the book called of .004. I’ve been told that was fine because old book said .010. I don’t want to chase something that doesn’t really matter but I also don’t want to wreak a 30k engine.

[Rawze]

If there are any loose springs in a scissor gear,.. it will eventually eat through the retaining screw and have a high possibility of destroying the entire front of the engine when it fails. - whenever someone comes here and does an inframe with me, I throw those things in the trash and put a regular gear there instead whenever possible. They really do not reduce noise to any measurable amount compared with the sound of the engine, and there is no less wear in engines with them than wothout.

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-- 90% of the time, when there is a medium-pitched gear hum that goes up and down with rpm on the ISX, ... it is the oil pump that is causing it, not anything in the gear train. When it starts to becomes louder than the engine at say, 20+ feet away or so, that is when someone should be concerned. - It is common for me to be able to walk across a truck stop parking lot and hear what trucks have a worn out oil pump.

[Magard]

It’s not a whine. And you can only hear it a idle. If you bump rpm up you don’t hear it anymore. It’s like a rattle. Really light sounding parts. At first I thought it was a belt or pully or a idler. I’ll bet it’s those springs. Do you know if I should be able to tell backlash if springs are still right. I’m gonna pull it apart I guess before long. I want my mechanics that I deal with to deal with there work. At least maybe will all learn something. They have already changed some of there practices.

[Unilevers]

the scissor gear itself runs fine unloaded with no tension, its the springs that come apart and fall into the gear train eventually from rattling around. Just stick a camera up in there you will be able to see if they are still loaded. if in doubt pull the cover off.

10 thou is fine for backlash. the book calls for 4 but older books used to call for 10.

[Magard]

I was able to see all the springs and feel for movement with screw driver with cover on. Everything looks good. I am starting to think it’s the idler gear that runs the cam. It’s supposed to be .004 on new specs. Old specs was .010. I’ll bet it was running at .004 before. It also goes away when you pour gear oil in while running or when oil temp is cold. It seems like compressor makes it more noisy. High idle can’t hear anything. Compressor nock keeps getting louder. I think compressor is sending pulsating load into gear train and making the idler gear make noise. I’m gonna run it some more. I’m super busy right now. Maybe change compressor this weekend. What is the failure rate of bearing in idler gear. It’s it a bushing with oil pressure. This noise could be a ocd thing on my part. I listen to every little thing. The noise seem to be coming from the front high left front right where idler gear is.

[Unilevers]

wheres my post about just roll the window up and drive it?

[Lonestar10]

And cryckee the mysterious wild uni strikes it's prey with venom and vigour and slides right back into hiding.

[Nostalgic]

(08-08-2019 )Magard Wrote:  This noise could be a ocd thing on my part. I listen to every little thing.

I'm glad I'm not the only one haha. Thinking back, I did it even as a company driver - it's just more expensive for me now when I obsess over the noises. In fairness, I do it to everything and it usually does eventually lead to something, which just increases the paranoia.

I need to spend more time in the dozer - it tends to numb one a little to all the clanks, grinds, and weird sounds haha.

[Mattman]

My opinion, if you hear a change its because there is something different. When you run a piece of equipment day after day and pay attention you will very quickly pick up on any noise or behavior that isn't normal.

Trust your gut.