Big drama - half the teeth are gone. What is this part in the 1st place? YD25 (photo)

[cesanneo2]

Hi all.
When replacing the timing chain I noticed, that the super important pair of gears in the area of the bottom chain, which are so crucial to be locked together... the narrow one lost half the gear teeth.
So i am quite sure it is out of sync now and I do not know even what this part is / what it does.
The small gear is very wobbly. I can basically pull it out to the level it won't even engage by the big gear on the top.
I wonder if you could help me out by telling what it is and hopefully linking to some good youtube videos on replacement or documents.
tia!

 

[cesanneo2]

Looks like it is scisor gear, part of idler gear. I found the video below.
There is no results when looking for parts. Is there any other name for it? Looks like it comes only as used whole units. Looks like a big job.
Would I need to undo the subframe? What if I just removed the big gear that drives them? I would be ok with a bit of shake for a while as long as I can move it to a garage where i could get the car up, source the parts and remove and replace what I need.
Btw - how bad is it without the balance shaft at all without balancing the engine prior?

 

[dagwill]

Hi doesnt sound good with teeth missing ?? what caused that in the first place ??,,,,,,, Im no expert and not saying my advice is correct. I believe Scissor gears are designed to minimise backlash and noise, I dont think running without it operating as it should will hurt anything [ short term ] probably the balancer as well. Just to get home or somewhere better to work on it.

 

[dagwill]

Rereading your post, it sounds like the scissor gear is coming apart,,,, a wild guess broken circlip. check that it wont let its innards springs etc. spew out into the rest of the timing chains/gears and cause a disaster. You may have caught it just in time.

 

[cesanneo2]

get home or somewhere better to work on it.

Thanks. That's the idea
So I was thinking about removing the cog wheel that drives it.
This will get out of time, but hence I would probably need to a) get rid of it totally b) replace - it will probably be out of time anyways and there must be a way to time it. There was something posted here and on YT.
Doubts I have: does it do anything else than balancing and improving comfort (and probably saving egine mounts)?
If I stop turning them, am I risking oil starvation? I read here that when removing there is an oil galley that should be plugged. (details in the thread below).
https://www.navaraforum.com/threads/yd25-balance-shaft-is-it-needed.38113/#post-407853That would also leave a gap between timing chain sprocket and oil pump. Oil pump being fixed and chain sprocket being tensioned and in line with the chain I woud also assume it won't move (worst case scenario some machined part or I could probably get the teeth machined off and get a new gear at some point (but the machining will be costly for sure and the steel is rather hard).
If it is safe (or at least no obvious reasons not to do it, I would go for removing this cog wheel to get it running).
I think I must be quite unlucky with that - there is close to zero information on that and no spare parts.

 

[cesanneo2]

Rereading your post, it sounds like the scissor gear is coming apart,,,, a wild guess broken circlip. check that it wont let its innards springs etc. spew out into the rest of the timing chains/gears and cause a disaster. You may have caught it just in time.

Yes - it has all fallen apart. I found one broken tooth just resting on a tensioner so it was flying all over the place. I removed the C clip hoping i could just get rid of that toothless gear, but no luck - it is secured by the bolt which looks impossible to remove until the whole unit comes off.

 

[Erick]

I would not even think of starting until all gears and bits are replaced. The consequences are horrific-complete destruction of engine. U might get away without pulling sump off to get all the bits out if u trust the oil filters, but a complete rebuild of the timing sequence, top and bottom as the stress caused by what has happened transmits through the whole system. Many ph calls to wreckers for gears and a couple new timing chains would be where I would start.

 

[cesanneo2]

I would not even think of starting until all gears and bits are replaced. The consequences are horrific-complete destruction of engine. U might get away without pulling sump off to get all the bits out if u trust the oil filters, but a complete rebuild of the timing sequence, top and bottom as the stress caused by what has happened transmits through the whole system. Many ph calls to wreckers for gears and a couple new timing chains would be where I would start.

Good pick.
Re timing chains - absolutely - I have all the parts waiting to put them in.
I just saw the damage on the balance shafts on the job of replacing the timing. The whole timing sequence will be replaced.
The main question because of new circumstances is: can I get away by doing only the timing and disconnecting the balance shaft?

 

[cesanneo2]

Hi doesnt sound good with teeth missing ?

It sounded like a bad metallic rattle. I was sure it is the timing chain rubbing against the casing and it was indeed very loose. I got the timing kit, bit of drama removing the harmonic balancer (850Nm electric impact wrench did the job, 200 Nm did not, 400Nm no idea - it did not fit).
After pulling the balancer and removing the cover I saw all that damage on the scisor gear. Tools down and wondering how to approach it. I would not mind if it wasn't as smooth, non-vibrating as a new one, but I wanted to pick some brains to know if the balancing shafts drive some vital organs of the engine It can be deleted with some proper procedures, I just do not know if it can be simply disconnected if broken.