Differential lock doesn't work?

California · Aug 6, 2012

This is the first clear picture I've ever seen showing how the YM differential lock mechanism works. I thought others might be interested.

I'm linking to relhogh's picture here, he posted it in his thread about repairing the brakes on his YM1500D Green.

The way the difflock works is sort of Mickey Mouse. Push the pedal under your right heel, that rotates the shaft going into the transmission. This forces the doubled rollpin to climb the ramps of the shifter fork. The fork then forces the diff lock collar sideways, engaging its pins into the recesses of the gear next to it.

This is notable to me because my YM186D needed this repaired before I put it in service. That ramp was worn away where the rollpin meets it, I think because the tractor was used for a couple of decades clearing snow and the operator was on the difflock pedal all the time. Welding some metal on the ramp (then grind/polish) to restore its shape was all it needed, now it's good again for many years.

And here's the badly worn ramp on my YM186D before repair.

206067d1301426408-trans-case-lock-seem-not-p1014683rworndiflockfork2.jpg

k0ua · Aug 6, 2012

Hey thanks for posting.. Now I know how that works.. I bet they are all about the same or nearly the same, and your description was good also. Again thanks.

James K0UA

Pete Judd · Aug 6, 2012

Thanks Cal, I know that I have a sheared roll pin on mine, and the pic lets me know what I am going to get into when I finally get around to fixing it.

relhogh · Aug 6, 2012

Hey California

Yea that also works it you pull up on the lever.
Dont know why they made it that way.

chriswheeler · Aug 7, 2012

Noticed mine when I had to pull the final drives out of my JD 950, same setup, yanmar made. Have to remove both left and right final drives to do anything with it. Drive for the right wheel ( dif lock ) is engaged by moving a coller when steping on the dif lock. This coller is spring loaded with 2 drive pins for the right wheel. When engaged, friction from the load on the pin drive keeps the drive pins in place. The moment that the load is off the pins, the spring disengages the drive unless you are still standing on the pedel. Almost fool proof, but the left wheel has to rotate some for the pins to engage the drive. I was that deep into mine to change a bad 3rd gear cluster, almost had to strip the whole case to get to it. Not much fun to work on.
Chris

ym165dpete · Aug 9, 2012

On my ym165d the shaft going through the finder was seized up . when I did my referb and paint ,it took a good long while to free it up.

California · Apr 28, 2015

Someone asked about the photo I included in the first post above. Something has gone wrong in the TBN database and old photos are no longer visible even though I can see this photo listed in my own Attachments history.

So here's a fresh link to show the same photo. I'll note I first posted it 3-29-2011 so that I can find it again if this link goes bad.

Pressing the difflock pedal pushes a rollpin against this ramp as described in the first post above, eventually causing the wear you see here. The previous owner used this YM186D mainly for blading snow. He must have been on that difflock pedal all the time.

Welding the fork back up and grinding it to its original shape restored the difflock function.

View attachment 422684

The fork is #85 in this Hoye diagram for YM2000. The V is hard to see but the double rollpin that bears against the V is obvious. Stepping on the pedal causes the fork to slide along the shaft that passes through it.
Yanmar Tractor Parts: TRANSMISSION_INTERNAL

smitty888 · Jun 12, 2022

@California, could you please repost those pictures again? I am needing to do this repair on my tractor, and I'd like to see what you did to yours. Unfortunately, the site says that they are no longer available.

Thank you!
-smitty888

California · Jun 12, 2022

They've been messing with the old archived stuff again!

I found the photo is still listed in my 'Attachments' and it was used in this 2011 post. Tell me if the photo and diagram are visible to you at this link:

Trans case lock seem not to work anymore

A few months ago It worked great when I had to cross one of my creeks, today, I had one wheel slipping and stomped the pedal, and it did not engage. I have not gone to the manual yet, and it was getting dark, the pedal stayed down and had to pull it up with my heel. Any thoughts? This is on a 186D

www.tractorbynet.com

The repaired shift fork is #12 in the diagram, and the worn area built up by welding is near the line drawn from '12' to the part.

Here's my photo again - before the worn spot was filled in by a weld.

ponytug · Jun 13, 2022

The photo and parts image are visible to me...

bmaverick · Jun 13, 2022

California said:
They've been messing with the old archived stuff again!

I found the photo is still listed in my 'Attachments' and it was used in this 2011 post. Tell me if the photo and diagram are visible to you at this link:

Trans case lock seem not to work anymore

A few months ago It worked great when I had to cross one of my creeks, today, I had one wheel slipping and stomped the pedal, and it did not engage. I have not gone to the manual yet, and it was getting dark, the pedal stayed down and had to pull it up with my heel. Any thoughts? This is on a 186D

www.tractorbynet.com

The repaired shift fork is #12 in the diagram, and the worn area built up by welding is near the line drawn from '12' to the part.

Here's my photo again - before the worn spot was filled in by a weld.

I like reading old threads. Something is there to glean from.

smitty888 · Jun 14, 2022

So, it appears that my situation is a little different than most. I did some testing with my YM2000 chained to a tree, and the diff lock did not work when I pressed the pedal down, but it did work when I pulled the pedal up. With this information, I figured that I was having the same issue as California.

I then pulled off the two U bolts to remove the right side fender. I had to undo the PTO linkage as it is part of the diff lock shaft, then I removed the snap ring holding the diff lock shaft in. I disconnected the 3 point lift arms at the end of the arms, not near the transmission of the tractor. I unbolted the hydraulic fluid feed at the top of the transmission case, then undid the 6 bolts holding the hydraulic piston system onto the gearbox of the tractor. After pulling that off, I had to drive out the roll pin in the diff lock lever on the outside of the transmission case so I could rotate the lever enough to get access to the roll pin on the inside of the transmission case. It was kind of a pain, but once I got it driven out, the diff lock shaft slid out of the transmission case. From there, I was able to remove the spring, then remove the diff lock shift fork.

I was surprised to find very minimal wear on the ramp of the shift fork, but pretty extreme wear on the contact face of the fork. Unfortunately, the wear resulted in a raised lip that dug into the piece that the fork mates with deep in the transmission. I went ahead and ordered a new shift fork from Hoye; I'm hoping the mating piece will be ok.

careyo63 · Jun 14, 2022

Haven't been inside mine to look at it. But it seems there was "alot" of pressure on it to cut that grove. For awhile. Well done!!..... And Welcome

smitty888 · Jun 17, 2022

Thank you for the warm welcome!

Unfortunately, I do not have great news. I paid $200 for the new differential lock shift fork and an extra $30 for 2 day shipping, and it showed up 4 days after I ordered it :/

Regardless, when it arrived, the whole part was painted. As I don't want paint chipping off in the transmission, I had to use a wire wheel to remove the paint from the surfaces that engage the differential lock collar. Additionally, because it was painted, it did not slide on to the differential lock shaft. After removing all the paint from the bore of the shift fork, it finally slid on. Unfortunately, the new shift fork cannot slide onto the differential lock collar because the top of the fork is taller than the original and hits the case inside. I think my only choice now is to grind it shorter until it fits.

In the midst of all this, the O ring on the differential lock shaft broke. Does anyone know what size this is?

I love Hoye and all that they do to keep old tractors working, but part quality is frustrating sometimes. Heads-up to anyone who orders one of these: it won't be a perfect fit and some modification will be necessary.

Update: I contacted Hoye, and they said they would address the problem Monday. They have really excellent customer service.

smitty888 · Jun 27, 2022

So for an update, Hoye and I went back and forth several times to try to figure out what was going on. Hoye requested a used shift fork from their boneyard and compared it with a new one identical to the one that they sent me. They claimed that both are the same size and that the part number is the correct part number from the manual.

They said that it looks like part 60 from this manual: TRANSMISSION_INTERNAL: Yanmar Tractor Parts could be worn from pictures that I sent, thus making the new part hard to fit correctly. I don't think this would result in what I was experiencing, but they suggested grinding down the top end of the shift fork to get it to fit. They suggested to be subtle on the grinding and check to fit often.

I went ahead and ground the topside of the shift fork until it slid into place, see picture below.

I used a flap disc and eventually got it ground enough. I used (2) #12 o-rings from Home Depot to replace the o rings on the diff lock pedal, measurements 5/8 in. I.D. x 13/16 in. O.D. x 3/32 in. wall thickness. These are ***-160 o-rings on Hoye's website. In order to get the compression spring that rides against the diff lock shift fork back into the transmission, I had to use a c-clamp to compress the spring. Once it was compressed, I was able to slide it off of the c clamp pad and against the shift fork. From there, it was a matter of installing the roll pins again and putting everything back together. Everything seemed to work ok, but it is yet to be tested. The diff lock shift fork was tight on the diff lock pedal, which has me a little worried.

bmaverick · Jun 27, 2022

smitty888 said:
So for an update, Hoye and I went back and forth several times to try to figure out what was going on. Hoye requested a used shift fork from their boneyard and compared it with a new one identical to the one that they sent me. They claimed that both are the same size and that the part number is the correct part number from the manual.

They said that it looks like part 60 from this manual: TRANSMISSION_INTERNAL: Yanmar Tractor Parts could be worn from pictures that I sent, thus making the new part hard to fit correctly. I don't think this would result in what I was experiencing, but they suggested grinding down the top end of the shift fork to get it to fit. They suggested to be subtle on the grinding and check to fit often.

I went ahead and ground the topside of the shift fork until it slid into place, see picture below.

View attachment 751718

I used a flap disc and eventually got it ground enough. I used (2) #12 o-rings from Home Depot to replace the o rings on the diff lock pedal, measurements 5/8 in. I.D. x 13/16 in. O.D. x 3/32 in. wall thickness. These are ***-160 o-rings on Hoye's website. In order to get the compression spring that rides against the diff lock shift fork back into the transmission, I had to use a c-clamp to compress the spring. Once it was compressed, I was able to slide it off of the c clamp pad and against the shift fork. From there, it was a matter of installing the roll pins again and putting everything back together. Everything seemed to work ok, but it is yet to be tested. The diff lock shift fork was tight on the diff lock pedal, which has me a little worried.

From the sounds of things, There could be an original Yanmar p/n then superseded by another Yanmar p/n. This isn't the first time something like this has happened. I would suppose Hoye's advice was more spot on to get things to work for you.

As your YM2000 has a US equal and there are 2 or 3 parts manuals and other changes over those model years, it's amazing you got a part to work.

There were Tree Frog green version and 2 Red Apple versions.

smitty888 · Feb 1, 2023

Unfortunately, I have more bad news on this.

My dad used the tractor to plow snow last week, and the diff lock did not work as it should. When pressing down or pulling up on the diff lock lever, the spinning tire on one side of the tractor merely switched to the other side.

For example, if the right side wheel is spinning and the diff lock lever gets depressed, the right side wheel will stop spinning and then the left side wheel will start spinning. I have not taken it apart to see what's wrong yet.

winston1 · Feb 1, 2023

Never heard of this before. It is normal for tire with least resistance to spin but when pressing differential lock both tires should spin. Your symptoms are very puzzling to me. I think your going to have to open up to get to the bottom of what is going on.

bmaverick · Feb 1, 2023

smitty888 said:
Unfortunately, I have more bad news on this.

My dad used the tractor to plow snow last week, and the diff lock did not work as it should. When pressing down or pulling up on the diff lock lever, the spinning tire on one side of the tractor merely switched to the other side.

For example, if the right side wheel is spinning and the diff lock lever gets depressed, the right side wheel will stop spinning and then the left side wheel will start spinning. I have not taken it apart to see what's wrong yet.

Sounds like the diff lock bridge for both is not engaging right, instead its just switching.