Yanmar 187D - 4WD just quit on me

[DWeinreich]

I've got a problem and maybe one of you will have the answer. I was pushing and pulling heavy snow around the yard with the front end loader with 4wd engaged. Something happened and now 4wd doesn't work when I go forward. There is a noise coming from the front axle assembly, possibly from where the drive shaft connects to the axle. The sound is like a gear that isn't engaging fully. The sound happens going forward, but not backward. I'm thinking something may have sheared off. The drive shaft still spins so the problem is somewhere forward of that.

If you have any clues or suggestions what to do to determine the cause and how to fix it I would appreciate hearing from you.

 

[clemsonfor]

Sounds like you need to tear into the axle. but jack up the front tires and spin one and see if the other spins, if not this will tell you something like a gear is busted so the front tires are no longer connected to each other. If one spins the drive shaft and the other dosent that front knuckle may be busted or stripped. Just start taking the axle apart and see. Cant screw anything up thats not already busted!

 

[California]

Could also be the point where the front u-joint attaches to the stub at the back of the front axle.

Early YM186D's (same axle?) had the front u-joint attached there with a rollpin which might act like a shear pin. Later ones were splined, so I doubt those could fail there.

But jack up the front end and turn the tires separately, together, etc to locate noise as Clemsonfor suggested. I hope your problem isn't in a hub.

 

[284 International]

Be careful when using the front drive shaft to assess whether 4 wheel drive engages or not. Even in a normally functioning unit, the drive shaft will spin, even in 2 wheel drive. All the shifter does is connect the transmission end of the drive shaft to an output coupling in the transmission housing. So, if there is a connection between the wheels and the drive shaft, and the tractor is moving, the drive shaft should spin.

Clemson and California already have said this, but here's a step by step procedure to isolate the trouble:

Jack the front of the tractor up, making sure everything is safely blocked. Place the tractor in 4 wheel drive.

Spin one of the front tires forward a few rotations, then backward a few rotations. The other side should spin equally but in opposite directions, and smoothly. The drive shaft should not spin. Do the same on the other side. Make sure everything feels smooth and equal side to side.

Then lower one side of the front axle until the tire is in firm contact with the ground. Pull on the top and sides of each the lifted tire to see if there is any wobble in the hub assembly. Now try to turn the tire. It should move only a fraction of a rotation, then hit solidly. You should not be able to turn the tire however hard you push. Be safe, don't knock the tractor off the jack stands.

Place the tractor in 2 wheel drive and do the same thing. The wheel should now spin freely and smoothly, along with the drive shaft. Repeat all of this on the other side, make sure to check in 2 wheel drive and 4 wheel drive.

Bowinelk had somewhat similar problems, found in this thread: http://www.tractorbynet.com/forums/yanmar/193620-240d-front-wheel-drive-not.html

In there are the ways to tell what area of the front wheel drive system isn't working.

Don't overlook the easy fixes, though. The 186D (Very similar to your 187D) I recently picked up for my school had intermittent four wheel drive. The detent that holds the coupler for the four wheel drive engagement wasn't working right, and there was some corrosion on the sliding gears. As a result, it would pop in and out of 4wd, and give a shuddering or grinding pop, and sometimes lurch in and out of gear.

Continual heavy lubrication for the last couple weeks and a partial tear-down fixed that, and now it engages and usually holds, and disengages smoothly as well. That's why it's smart to test the front axle with one side on the ground, to see where the trouble can be localized. It wasn't super easy, but it was much better than having to do a front axle rebuild.

Good luck, as things develop keep us informed.

 

[DWeinreich]

I did some of the tests you-all suggested and it seems the front wheels are still linked. Rotate one and the other counter-rotates. Blocked one and the other held firm. Found evidence of the trouble (see photos): there are four bolts holding the "pinion holder" (part 37) to the "axle case"(part 33). The two lower bolt flanges of the pinion holder are cracked off and the pinion holder is no longer in perfect alignment with its seat on the axle case. The two remaining bolts at the top won't hold parts together properly.

When I hold the pinion holder tight to its seat (just tested this with the two remaining bolts torques down and the shims, about 1mm, removed) all the gears seemed to mesh. If the bolts back out even a bit (1/16"-1/8") or the pinion holder is at all out of alignment the gears don't engage properly and I hear the sound of grinding gears.

When I disconnected the pinion holder I thought the pinion would pull out but there that's pretty big bearing that is too large to exit the rear of the axle case, so I cannot see the condition of the gears inside. I could see a damaged snap ring on the shaft between the metal ring (bearing) and the shaft inside the pinion holder. It must have been pushed off whatever groove it was in and is just riding on the shaft loosely doing nothing. It slid away and I can't get at it to show you.

Any thoughts on what to do next? Get someone to weld the flanges back on? Pull the whole axle off and take the works to a machinery service center?

 

[clemsonfor]

Id figure it out, how to take it apart, inspect all the pieces and then get someone to weld that flange up prfessionally, and replace the damaged or worn parts. But your going to have to dig at it and figure what holds what in place and get inventive, unless someone with personal exp taking that apart chimes in.

 

[California]

Ouch. I don't see how anything short of replacing the tailshaft housing ("pinion holder") would restore original strength.

If you simply can't obtain that part - is there enough meat left for a blacksmith to fabricate a strap across there that transfers the bolt stress to the remaining good iron? I don't see how just welding the ears back on would be sufficient.

Comment: PNG files are lossless, but huge and slow to download. Is there any way you could save future reduced-size copies as .jpg? They would be a tenth the size but should look just as good. Thanks!

Others can comment on dealers who have boneyards out back. Hoyetractor and maybe PEQ (hey Danny - hire some kid to finish that website!) are the only ones I am aware of.

I'll send you a PM showing some guy in Oregon who put up a Craigslist ad last October saying he was scrapping some Yanmars. I don't know what models, or what he has left now.

 

[winston1]

I know pictures can be decieving but it sure looks like that bearing is about the same od as the opening. Not meaning to question you, just asking if it could be a slide fit in that housing? You have a nice drawing of the outside, do you not have a drawing of the inside? For sure a used tailshaft housing would be the best solution. If one is not available a "good" welder can do a lot.
OK, after a little more thought, I believe you can remove the u joint, remove a nut or whatever is on the pinion shaft and probably a seal, then snap ring against a bearing and then slide the pinion housing off of the pinion shaft. The bearing will come off with it. Talking about an outer bearing now.

 

[DWeinreich]

Thanks Winston1 and California. I tried to work that bearing out through the hole - they are nearly the same size but it wouldn't come through. I may try one more time. The strap idea may work. There's a little "meat" on the pinion holder left that the strap could grab. The other thing I might try is to fabricate a collar around the pinion holder, and make it out of epoxy resin and carbon fiber or Kevlar fiber. With longer bolts it might work.

The other thought is to simply weld the pinion holder to the axle casing. I know this sounds weird but if it ever has to come apart again the weld can be ground off. As long as the rubber O-ring seal doesn't get cooked from the welding this might work. Maybe a MIG or TIG welder would run cool enough.

Please let me know if either idea makes sense. Getting the tractor to a shop involves 40 miles of driving with a trailer, and I don't have a trailer.

Getting the pinion holder off the shaft by removing the rear nut looked risky- the nut is held in place by a special washer that engages the shaft spline groove. The washer has six tabs that are folded up against the six faces of the nut so it cannot turn. I'm guessing that this nut also controls how far in or out the pinion gear is set against a bevel gear. In other words it's a factory-set tolerance.

 

[winston1]

You are probaby right about the setting on the pinion shaft. You can adjust that when putting it back by simply feeling the back lash between the pinion and ring gear. As long as you allow just a little back lash you would be OK. I got this idea from looking at a John Deere drawing of a 650 which has that same set up.