Yanmar YM1510D – Front Wheel Assist Not Working

[YanmarMatt]

I’m having an issue with the front wheel assist (4WD) on my Yanmar YM1510D and could really use your insights. Here’s the situation:

When I jack up the front of the tractor, I can spin one front wheel by hand and the other turns in the opposite direction, but it seems like it takes a minute to “catch”.


I also occasionally hear a metal-on-metal grinding sound, but it’s not overly loud or constant. Just enough to make me concerned. It doesn’t clunk or pop; more like a soft grinding that comes and goes.


Leaking + Low Fluid


The front axle fluid is definitely low, and I suspect a leaky gasket or seal. I have noticeable oil residue inside both front wheels, so I think fluid is leaking from the hub area or knuckles. I haven’t cracked anything open yet, but I assume this could be contributing to the problem — potentially insufficient lubrication of gears.

When It Started

This issue began while I was hauling and spreading rock, so the front end was under load. That’s when I first noticed the delayed engagement and the occasional noise. Before that, 4WD seemed to operate normal.

Tests So Far

• With the front lifted, both wheels turn opposite directions — no obvious binding.
• I haven’t drained the fluid yet to check for shavings or signs of damage.
• I haven’t opened the front differential or center joint yet either.

Looking for Advice

I’m hoping it’s not a stripped gear or something major. I’d really appreciate advice on:

• Whether this sounds like normal open diff behavior or a sign of internal wear
• How critical it is to fix the leak before diagnosing further. Any insight on how to fix the leak as well.
• What internal parts could cause this delayed front axle engagement
• Any tips on what to look for if I open up the front axle or center drive shaft

Thanks in advance for any help you can offer. I’ll try to get some photos of the leak area if that helps. Let me know if I should try any specific test or inspection.

— Matt

 

[winston1]

I would think there is a problem. There should be minimal slack when rotating tires. Only caused from minimal gear backlash. My first thought would be differential spider gears but I won't try to speculate on exactly what is causing your excess movement.

 

[bmaverick]

I’m having an issue with the front wheel assist (4WD) on my Yanmar YM1510D and could really use your insights. Here’s the situation:

When I jack up the front of the tractor, I can spin one front wheel by hand and the other turns in the opposite direction, but it seems like it takes a minute to “catch”.


I also occasionally hear a metal-on-metal grinding sound, but it’s not overly loud or constant. Just enough to make me concerned. It doesn’t clunk or pop; more like a soft grinding that comes and goes.


Leaking + Low Fluid


The front axle fluid is definitely low, and I suspect a leaky gasket or seal. I have noticeable oil residue inside both front wheels, so I think fluid is leaking from the hub area or knuckles. I haven’t cracked anything open yet, but I assume this could be contributing to the problem — potentially insufficient lubrication of gears.

When It Started

This issue began while I was hauling and spreading rock, so the front end was under load. That’s when I first noticed the delayed engagement and the occasional noise. Before that, 4WD seemed to operate normal.

Tests So Far

• With the front lifted, both wheels turn opposite directions — no obvious binding.
• I haven’t drained the fluid yet to check for shavings or signs of damage.
• I haven’t opened the front differential or center joint yet either.

Looking for Advice

I’m hoping it’s not a stripped gear or something major. I’d really appreciate advice on:

• Whether this sounds like normal open diff behavior or a sign of internal wear
• How critical it is to fix the leak before diagnosing further. Any insight on how to fix the leak as well.
• What internal parts could cause this delayed front axle engagement
• Any tips on what to look for if I open up the front axle or center drive shaft

Thanks in advance for any help you can offer. I’ll try to get some photos of the leak area if that helps. Let me know if I should try any specific test or inspection.

— MattView attachment 3825593

See this thread for helps.

2310D Knuckle Seal Replacement

Looks to be time to replace one of the knuckle seals since it's leaking pretty good now. Just ordered the seal and the process looks pretty simple, any concerns dropping the lower axle housing or just have at it.

www.tractorbynet.com

 

[AaronM]

I’m hoping it’s not a stripped gear or something major. I’d really appreciate advice on:

• Whether this sounds like normal open diff behavior or a sign of internal wear
• How critical it is to fix the leak before diagnosing further. Any insight on how to fix the leak as well.
• What internal parts could cause this delayed front axle engagement
• Any tips on what to look for if I open up the front axle or center drive shaft

The wheels spinning opposite directions when the 4wd input shaft is unable to turn is normal. If the 4wd shaft is allowed to turn then both front wheels can (but still might not) spin the same direction. If by "a minute" you mean less than a revolution then the delay could be caused by a loose or broken U-joint allowing the driveshaft to spin a little bit before stopping. This can cause a grinding metal sound from the bad bearings and can even let the shaft contact the metal shroud causing a metallic sound. If you mean you actually have to spin the wheel multiple revolutions then it sounds like a gear has probably lost some teeth. Just a guess though.

I, personally, would not worry about the leak until I got the main problem diagnosed & fixed.

The driveshaft U-Joint would be my first suspect. If it was an internal gear then I think you would have a different set of symptoms (grinding, binding, popping, slipping). It could also be a bad or broken bearing letting things get a little loose but I think you would have more serious symptoms.

The U-Joint can be seen just by removing the 4wd driveshaft cover. If you have to take apart the differential or knuckles then just look for any metal pieces, or missing teeth on gears, or anything loose that should not be.

Running those axle low on oil (or with bad sounds) is really risky. There are a couple gears in there that are very hard to find and you do not want to damage them.

Hope this helps

Aaron

 

[California]

And those U-Joints are near impossible to find. I discovered they were also used for a couple of years on the rear axles of a Honda ATV - and cost less, purchased that way.

I looked up my 2009 notes for the previous YM186D (no loader) that I sold several years ago:

HONDA ATV models:
1985 ODYSSEY (FL350) REAR SHAFT
Part # ATV300 $249
* These may fit other Arctic Cat models.

Or Ebay:
American CV
1985 ODYSSEY (FL350) Rear Axle Shafts Standard U-Joint
Price: $29.95 [in 2009]

 

[careyo63]

1510D bearings and seals.

 

[YanmarMatt]

The wheels spinning opposite directions when the 4wd input shaft is unable to turn is normal. If the 4wd shaft is allowed to turn then both front wheels can (but still might not) spin the same direction. If by "a minute" you mean less than a revolution then the delay could be caused by a loose or broken U-joint allowing the driveshaft to spin a little bit before stopping. This can cause a grinding metal sound from the bad bearings and can even let the shaft contact the metal shroud causing a metallic sound. If you mean you actually have to spin the wheel multiple revolutions then it sounds like a gear has probably lost some teeth. Just a guess though.

I, personally, would not worry about the leak until I got the main problem diagnosed & fixed.

The driveshaft U-Joint would be my first suspect. If it was an internal gear then I think you would have a different set of symptoms (grinding, binding, popping, slipping). It could also be a bad or broken bearing letting things get a little loose but I think you would have more serious symptoms.

The U-Joint can be seen just by removing the 4wd driveshaft cover. If you have to take apart the differential or knuckles then just look for any metal pieces, or missing teeth on gears, or anything loose that should not be.

Running those axle low on oil (or with bad sounds) is really risky. There are a couple gears in there that are very hard to find and you do not want to damage them.

Hope this helps

Aaron

Thanks for the insight. I progressed through your suggestions then found these gears on both left and right with some teeth missing. In a quick search this seems to be one of the hard parts to find, correct? Part #194441‑13950 I believe it is called the front‑final drive bevel gear. I reached out to lens12 as I saw he may have had some machined at one point. Any other ideas how to locate two of these?

 

[careyo63]

My guess the YM1500 and the YM1510 uses the same Gears. The 1510 does not show up in my book. So many models listed. Fredricks Importing parts. Try them they may have it.

 

[AaronM]

Unfortunately that gear is only used on the YM1510D. I really don't think that one looks like it would cause the problem you described though. If it were me, and I could not find a replacement, I would use it. Just file down the rough/thin edges so they didn't keep chipping off, make sure the mating gear looked OK, and that there were not any metal chunks still in there. There is still a lot of good contact area on each tooth and those gears don't spin very fast.

 

[careyo63]

Interesting! The YM2000D and the And the YM2010D use the same Gear, front axel. . SG-1352 YM195-2420 no Ym1500 etc.. Better get a good file!

 

[ponytug]

Thanks for the insight. I progressed through your suggestions then found these gears on both left and right with some teeth missing. In a quick search this seems to be one of the hard parts to find, correct? Part #194441‑13950 I believe it is called the front‑final drive bevel gear. I reached out to lens12 as I saw he may have had some machined at one point. Any other ideas how to locate two of these?

That's a very odd failure pattern. Have you found a chunk of metal there? Or at least filings? Were the front axles grossly loose?

If you can't find replacements, I'd take it to a machine shop to see if they can fill in the holes. In the reassembly, if it were me, I would make sure that I had the gears shimmed correctly to mate properly.

All the best,

Peter

 

[California]

Unfortunately that gear is only used on the YM1510D.

Does the US twin, the YM186D, use the same gears? Now you have me spooked if those bevel gars are irreplaceable.

Running entirely on soft and sloping orchard ground, I almost never shift out of 4x4 - only when I (rarely) go out onto the hardpacked lane.

 

[YanmarMatt]

That's a very odd failure pattern. Have you found a chunk of metal there? Or at least filings? Were the front axles grossly loose?

If you can't find replacements, I'd take it to a machine shop to see if they can fill in the holes. In the reassembly, if it were me, I would make sure that I had the gears shimmed correctly to mate properly.

All the best,

Peter

There were some filings and chunks. I’m trying to find a machine shop that may be able to weld it up, then machine it down.

When I would spin the left wheel I could spin it almost an entire revolution before the right wheel would engage. Whereas the same test on rear wheels engages immediately. If that’s what you mean by loose then yes they were loose!

If anyone has a good machine shop I’m happy to ship the parts. It’s not time critical that this gets fixed. I’m in AZ so it’s still 110 degrees. I’ve got a few months until tractor season.

 

[YanmarMatt]

Does the US twin, the YM186D, use the same gears? Now you have me spooked if those bevel gars are irreplaceable.

Running entirely on soft and sloping orchard ground, I almost never shift out of 4x4 - only when I (rarely) go out onto the hardpacked lane.

My 4 wheel drive engage lever broke so I typically always keep it in 4 wheel drive, but I may need to fix the lever to take it out when not needed. Most of my work is on dirt, but it broke when I was moving rock for a friend.

 

[ponytug]

There are a fair few machinists here, but I would look locally first.

I'm having trouble visualizing what could cause one to be able to spin a wheel 360 degrees before the other wheel began to turn.

All the best,

Peter

 

[winston1]

For what it is worth I agree with Aarons suggestion.

 

[AaronM]

Does the US twin, the YM186D, use the same gears? Now you have me spooked if those bevel gars are irreplaceable.

Running entirely on soft and sloping orchard ground, I almost never shift out of 4x4 - only when I (rarely) go out onto the hardpacked lane.

Surprisingly the 186D uses a completely different 4wd axle design. I don't think they share a single part.

Aaron

 

[California]

Surprisingly the 186D uses a completely different 4wd axle design. I don't think they share a single part.

Aaron

Thanks Aaron. I had read that the US YM186D has a heavier front axle to make it suitable for loader use. This is the first time I've seen confirmation that they are different.

 

[Oz_Kioti]

This won't help the OP, except maybe for the fact that my problem was down to the operator - me!

Tractor was LG47hp (LG now LS) and I abused the front axle by asking the FEL to do what it wasn't designed to do, placing horrendous down loads on the front axle, and REALLY subjecting the forks on the FEL to horrendous shocks to try to jerk out tree stumps which demanded something beefier than a 47hp tractor!

Covid BS had just hit at the time, and getting parts out of Korea was just not going to happen. Dr Google located two new bevel gears from a dealership in Missouri which a friend shipped over to me, and from my searching, they were the only two new ones in existence. Maybe the factory might have been able to assist, but the Australian importer couldn't even get LS to talk to him at the time!

They were in a bad way:

 

[YanmarMatt]

Update:

Thanks again, everyone, for all your help so far. It’s been reassuring to know that I can ask questions here and get such thoughtful advice.

I was working on my tractor again today and wanted to share what I’ve found:

• I removed the left axle cover to check for stripped gears—so far, nothing looks destroyed in there.
• I pulled the driveshaft, and the lower U-joint looks a bit scuffed up. It’s not completely broken, but I think I’ll go ahead and replace it.
• One thing I’m still debating: On the front differential, where the driveshaft connects—if I spin that input gear, I would expect the axle spindles to turn. However, they’re not.
• Looking behind the left plate, I can see a gear spinning, so something is moving internally.

My main question now: Is there some sort of clutch or mechanism in the front differential that engages the wheels? If so, I’d like to understand how it’s supposed to work so I can troubleshoot more effectively.

So far, I’m encouraged not to have found any completely destroyed gears—just the chipped

gear I posted about earlier and the U-joint that needs replacing. If anyone can help me identify how this front differential functions, I’d really appreciate it.

Thanks again for all the guidance.

— Matthew