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F20d 4 x 4

P

passy-HT

Member
Hi, I have just bought an F20d and am not sure if I have been stitched up ! It was at an auction in Suffolk UK. I had a chance to start it and put it in gear to drive it a few feet forwards and backwards. When I got the tractor home, most of our land is on a slope I found that only the front wheels are being driven. All the labels are in Japanese but I am sure that i have found the 4x4 lever and although it will move it will not disengage and lock into the second position. Can someone please tell me that I am being thick and all i need to do is wiggle something else or have I bought a pup ?
 
If only the front wheels are being driven then you likely have a broken rear ring and/or pinion gear. That was a weak link on that tractor and is fairly common if the tractor is abused. There are no shifters or settings that will engage only the front wheels.
 
Hi Arron / Winston. Thanks for the reply. More questions for you. The tractor starts and runs ok, drives ok with no nasty noises but lacks a bit of traction as I am relying on the front wheels to do all the work. Can I carry on using it as is or am I doing more damage ? I have some basic mechanical skills is splitting the tractor and replacing the parts something I could attempt or is that " expert level " stuff ?
 
Tractor split is not necessary to access the pinion and ring gear but removal of a bunch of sheet metal, seat, hydraulic unit is necessary. The one I worked on had one tooth missing on the ring gear and some ring gear bolts sheared and others completely backed out. Don't know how that happened but it did. The ring gear was just spinning freely on the differential carrier. It did run without noise. Not knowing exactly what is going on with yours I would recommend not using it. Just my 2 cents.

Wondering if you have been running yours without an over run clutch on the pto??
 
Hi Winston, I am very much a newbie to this. What is an overun clutch ? I just have the PTO shaft coming out of the back of the rear of the tractor. I apologise in advance for my lack on knowledge.
 
This is an over run clutch. http://www.hoyetractor.com/PROD/OR-660.htm

It allows your pto to free wheel when you stop your tractor. Tractor Ernie, a former tractor dealer and very sharp on these old tractors believes running without an overrun clutch on these is possibly the cause of knocking out the ring and pinion on these models. I know the one I worked on did not have an over run clutch. It does now. You need one for safety if no other reason if using a rotary mower or any pto driven implement that has flywheel momentum.
 
I did not know about the o-r clutch protecting drive gears. Mine came with a factory o-r clutch; don't know if that's because it's an export model.
 
I believe all the export models have the internal over run clutch. Talking about the old export models, pretty sure the new generation has live pto's. I tried to find tractor Ernies comment on it but unsuccessful so far.
 
Hi Winston,

just looked at the picture of the overrun clutch. That makes a lot of sense as I can see with a bush hog running there will be a lot of inertia with the heavy blade spinning. I think next step will to be to get a service manual from Hoye's and get the tractor into the shed and start having a proper look.
 
So I have now bought a parts book from Hoye in the USA. All in Japanese but has a lot of very good diagrams and I can now identify the correct part numbers if I need to order anything. So as mentioned earlier in the thread I have no drive to the rear wheels with only the front ones being driven. The gear selector will move but will not get into position to lock in Just the back wheels. When I drive the tractor it sounds very smooth with no grinding or rumbling. How do I get to the ring gear ? is it directly under the seat ( IE removing all the tin work and I think the hydraulic pump ? ) or do I approach from another direction ? With the gear selector not locking into position does that point to another issue or is that just a symptom of the ring gear being stripped ?
 
The only factory manuals for non-export models are in Japanese (which work pretty well for the parts one), so English versions of the operators and service ones have been attempted. Google "murray manuals yanmar" to see if there's one for yours, and if so, Hoye would stock it, I think at $40.
 
<QUOTE author="winston"><s>
</s>For what it's worth I will attach a thread I participated in when changing out the ring gear on an FX24D. Yours likely very similar. Long thread but numerous pictures that could help you. <LINK_TEXT text="http://www.tractor...055-drive-train-yanmar-fx24d.html</LINK_TEXT><e>
Click to expand...
/e></QUOTE>

For what it is worth I don't think the 276 manual is going to be much help on the rear axle. Not very similar. Parts manual, common sense, asking questions, probably better. On the other hand the parts manual will be very valuable.
 
<QUOTE author="winston"><s>
</s><QUOTE author="winston"><s>
</s>For what it's worth I will attach a thread I participated in when changing out the ring gear on an FX24D. Yours likely very similar. Long thread but numerous pictures that could help you. <LINK_TEXT text="http://www.tractor...055-drive-train-yanmar-fx24d.html</LINK_TEXT><e>
Click to expand...
/e></QUOTE>

Lastly, please don't tear it down unless your completely comfortable where the problem is. I don't claim to be an expert at analyzing even though I may sometimes come across that way. I sure don't want to be guilty of causing you more grief. Best of luck whatever you decide.

Sorry about all the excess. One of the side effects of getting old.
Click to expand...
 
Just read that loooooong post Winston. Great story with some wonderful pictures. The symptoms seem to fit my tractor exactly. One point was raised where someone mentioned about an option were only the front wheels could be driven to add tight turns. Guess I wouldn't be lucky enough to have bought that model.....
 
Assuming you are stuck with it,before jumping into the ring and pinion, I would find out why you can't get out of FWD. If no drive, then engage diff. lock and see if it moves. Meanwhile, be aware that you are only driving on 1 lightweight front wheel assembly at a time.
 
I have now got the tractor into the workshop ( old stable...) and have started the tear down. I have got most of the tin work off just got a stubborn rubber knob on the control for the three point linkage that will not come off ( guess a bit of heat will soften that up. ) stopping me from lifting the seat panel off. I can then give it all a good wash down before going any further. Will try and load some pics up when my daughter can tell me how to lower the resolution....
 
You really should do more troubleshooting before jumping into that ring and pinion. Although they are suspect, there are other reasons. . . . .
 
Hi Norm, I am all a bit new to this so please excuse my lack of knowledge. AT this stage I have only just stripped away the tin work and am about to give everything a good wash down before I start the serious stuff. I was interested to see what you said about only one front wheel being driven as I had noticed today when I was testing it in the field that with the handbrake on only one front wheel was spinning in the mud. IS the diff lock the pedal at your heel down on the right hand side ? if so this did not appear to have any effect. Before I start " open heart surgery " on her, is there anything else I should test ?
 
Ok pic one shows my F20D before starting work and Pic two shows her with most of the tinware removed.

38451_40438368b001a85ae78430d54aeac913.jpg


38451_162a79b8e0adb254b68914651b081b00.jpg
 
<QUOTE author="passy"><s>
</s>Hi Norm, I am all a bit new to this so please excuse my lack of knowledge. AT this stage I have only just stripped away the tin work and am about to give everything a good wash down before I start the serious stuff. I was interested to see what you said about only one front wheel being driven as I had noticed today when I was testing it in the field that with the handbrake on only one front wheel was spinning in the mud. IS the diff lock the pedal at your heel down on the right hand side ? if so this did not appear to have any effect. Before I start " open heart surgery " on her, is there anything else I should test ?<e>
Click to expand...
/e></QUOTE>

There is no differential lock on the front axle. The pedal is for the rear wheels. The front wheel with the least resistance will spin. That is normal.
 
If no rear drive with diff. lock engaged then might's well check ring an pinion. You were questioning operating with only front drive, a good way to destroy it. You app. still have prob. of turning off FWD.
 
Hi Guys need your help again. I have now stripped off all the tinwork and cleaned the gearbox back axle area. I have undone the 9 bolts and the one nut hidden under the hydraulic pump. I have disconnected the handbrake and over levers that are mounted on the upper housing that I need to lift off to view the ring gear Below. Problem is I cant shift the upper housing. Is it just a case of giving it a tap with a mallet around the joint or have I missed something ?

38451_189bf140e68b12da846c10cc175cddfe.jpg


38451_4ae46e7050179a0a80f58245f586f559.jpg
 
The housing has a couple of dowel pins that will allow it to move only straight up. The gasket will also likely stick it somewhat. I would tap around it real good, then use a sharpened tool to get between the housing and cover. Likely have to use a hammer to drive it in just a little. Take your time, once it starts coming up a little at any point then work your way around it bringing it straight up and not cocking.

That cover will be heavy so be ready.
 
Ok we are getting somewhere now. large casting has now been lifted off ( you weren't joking Winston when you said that was going to be heavy ! ) I ended up refitting the upper three point linkage upside down so that it only went into the top casting and then used a trolley jack to push against it. Popped off a treat. I have checked the ring gear and there are no bolt heads showing at all on the reverse and it spins freely. Guess they have all sheared off and are sitting in the bottom of the sump ? The ring gear appears to be undamaged and the pinion gear appears to be in good condition. Next thing to do will be drain the oil and then get the wheels off and get it jacked up ready for next weekend when I can take the two rear axles off and remove the diff. What do you think the chances of reusing that ring gear is going to be when I have got it stripped and can see the reverse ?

38451_2b7a9e2433635d3cdef69471ada595bc.jpg


38451_23b2d0089c7ae0e909fa465b4e3cc819.jpg
 
"If" the bolts are all stripped and no gear damage it might be possible to put new bolts in and go back together. I think the right axle is the only one you would have to remove in order to get the differential out.

I suspect high speed shifting and or not overrun clutch on the pto stripped the bolts. If you could get by with only new bolts you would be lucky. Make sure you look at all pinion and ring gear teeth closely.
 
Thanks for the reply Winston. It will be a week now before I can get back on to it when I will focus on removing the axle and then trying to get the ring gear out onto the bench. Checking the pinion and ring gear in situ they both look surprisingly good. I am a bit worried about were those sheared bolt heads have disappeared of too.
 
It appears to be a common problem with that series of tractors. Wonder if they used a softer grade of bolt? Winston do you remember what was on the heads of the bolts you retrieved from the FX you did?
 
<QUOTE author="PaulW"><s>
</s>It appears to be a common problem with that series of tractors. Wonder if they used a softer grade of bolt? Winston do you remember what was on the heads of the bolts you retrieved from the FX you did?<e>
Click to expand...
/e></QUOTE>

Seven.
 
Do I need to buy "special" bolts to fit the ring gear back onto the mounting plate ? are they shear bolts designed to break underload and protect the rest of the drive train or just too soft for the job ? I will be back in the workshop next weekend when I will be taking off the axle and hopefully removing the complete diff and starting the hunt for the missing bolt heads.
 
When you find the missing bolts there should be a number stamped on the heads. Likely a 7 which stands for grade 7. I guess you could call them special.
Yanmar part number for the FX24D is 26016-080202, they are M8-20. Yours might or might not be the same. My memory is not real good but I am thinking I bought some at a fastener company like Fastenal or such.

I also don't remember whether they are course or fine thread, likely 1.25 or 1.0 pitch
 
I'd imagine they would be fine threads but check this first, secondly I'd also up that to a grade 8 if it were mine. Use loctite on them too.
 
Couldn't resist it this evening so popped into the workshop and had a quick fish around in the gearbox and pulled out the first of what should be I think 8 sheered bolts hiding down there. As Winston suggested, the head of the bolt has a 7 on it. 8 more to go......

38451_911b4d1352a786cef3625bb56ec81d43.jpg


38451_f5c5e82769a09bfb52d8fd270038f2ee.jpg
 
Winston, my mechanic skills are very low, this is the first major strip down that I have attempted ( apart from some very old English BSA motorcycles ) so any of your advice is very well received and much appreciated. I am sure that by the end of the weekend I will have a whole new list of questions for you guys on here !
 
Mmm looks well mashed up eh? <E>:shock:</E> Looks to be badly bent too. If it looks internally all OK (check this well as that looks to have been crunched between something) and the crown wheel is able to be re-used run grade 8's and loctite would be my suggestion.
 
Hi Guys, more questions for you.

I need to fish out the remaining sheared off bolts from the diff ring gear that are sitting in the sump of the gearbox. Looking down through the dip stick filler hole I can see the end of one and I suspect the rest of them are all down there together. I am going to pop down to the hardware shop tomorrow and get one of those magnet on-a-pole tools and have a go with that. The question is, is there a better angle to go in from or am I stuck just fishing blind through the filler hole ? Next question. I need to remove the diff to get the ring gear off. Can I just undo and pull away the righthand axle and the remove the diff or do I need to remove both axles ? Last question for today, what grade of oil do I need to get to fill the gear box back up with assuming that all this has a happy ending ?
 
The FX24D differentail could be removed by just removing the right axle. I would think yours to be the same.

I believe removing the suction strainer on the right hand side might give you another opening to fish through. the strainer needs to be removed and cleaned anyway.

I have use Walmarts Supertech transmission/hydraulic oil and have used Tractor Supplys Traveler brand transmission/hydraulic oil. Here are the specs for your lubes. <LINK_TEXT text="http://www.hoyetra...pport/knowledgebase.php?article=1</LINK_TEXT>
 
Fished out some more bolts from the sump. I now have a total of 5 with there spring washers. But no sign of the other 3 ( I think there is 8 in total )

38451_9670ed6abcd3db843ba70135810d719b.jpg
 
<QUOTE author="winston"><s>
</s>I am guessing that is a 1.25 thread pitch. You probably know but that indicates 1.25mm between threads.<e>
Click to expand...
/e></QUOTE>

That bolt did not fail, it loosened and backed out until it beat itself to death. The stock bolt , with Loctite should be fine.
 
Removed the gearbox filter to gain better access to the sheered bolts and it certainly does need a clean up.

38451_dc02dea4d862628a604ae4ef7827d17a.jpg
 
Ok need some more help please. I need to get to the ring gear on the diff to replace the sheared bolts. To do this I am trying to remove the right hand axle. I have removed all the bolts that I can see and the Diff lock lever. The thing is stuck solid and will not move. Any ideas ? As I am only trying to remove the diff can I undo the housing that the wheel mounts onto and then slide out the half shaft freeing the diff that appears to only be mounted on a splined shaft.

38451_9c6e1cc3bb6a48f4184ccb469ab64c85.jpg
 
There will be dowel pins holding the axle housing in an exact location. The gasket will also be stuck. It is my belief your axe shaft is splined and should come right out of the differential. The shaft should pull out of the differential side gear.
 
Hi Winston,

looking at the parts book there appears to be a splined half shaft that just drives the gear in the axle. tomorrow I will try and take the large plate that has the wheel hub on off and see if I can slide out the half shaft. Do you think I will need to do this to both axles to be able to lift the diff out ?
 
If you go back and look at the pictures I posted from the FX24D thread you can see the splined axle shaft sticking through the gear. I can't see yours from here but just guessing it is the same. Without being there or better pictures I can't give any better advice. Going to a funeral, be back in a couple of hours. I still believe the whole axle housing should come right off.
 
Axle has now been removed ! just as Winston said it was just stuck down well. I am pretty sure that this is the first time that the tractor has been stripped down, all the bolt heads are untouched and most still have paint on them. After struggling trying to tap it and pull it I got a small scissor car jack and with a bit of wood as packing simply pushed the axle off, worked a treat. I did have to remove the second axle as the splined shaft was still holding the diff in place but with that removed it simply lifted out.
 
Diff is now out and on the work bench. Ring gear shows the remaining stubs of the sheared bolts, these easily came out just by tapping them round with a pointed bradle.

38451_fff379e7dc6d1be764ac69fac1d4e0f3.jpg


38451_f175c2cf356eef6b9b5a7fee0e7b447f.jpg
 
The ring gear appears to be in almost perfect condition with even the threads on the back usable. The pinion gear also looks good. Is there anything else that needs inspecting prior to rebuild or is the damage likely to be focused purely on the ring and pinion gear.
 
and now the fun starts. I have fished out most of the missing bolts and matched them up but am missing two halfs. the search continues......

38451_864343f2ca0272c1910e60c7de22d931.jpg
 
Very poor workmanship for a Japanese, (or any), factory. Don't they have Loctite thread sealer over there. I have read of the happening a couple of times over the years.
 
<QUOTE author="passy"><s>
</s>The ring gear appears to be in almost perfect condition with even the threads on the back usable. The pinion gear also looks good. Is there anything else that needs inspecting prior to rebuild or is the damage likely to be focused purely on the ring and pinion gear.<e>
Click to expand...
/e></QUOTE>

I would go back together with it. Looks to me like shock load caused bolts to loosen/shear. I would locktight as Paulw suggested and install an overrun clutch for mower usage. The 276 service manual shows m8 bolts on the ring gear and a torque value of 43 ft lbs. Would also try to put the ring gear on the carrier in the same bolt holes it came off. Manual suggests this. For what it is worth the 276 manual does suggest using locktite.
 
I am a bit stuck now. strip down has gone well and I am almost to the point where I can start the rebuild but I cant find the last two remaining bolt heads that must be hiding in the gearbox / sump somewhere. Question is I am going in through the dipstick hole and the oil filter hole on the side with my magnet. is there another chamber behind the next bulkhead I need to get access to or is that the clutch housing and will be dry so now way that the bolt heads could have worked they way to ? I am getting close to thinking I can rebuild with out tracking the two missing bolt heads down but I know that is taking a big risk of them suddenly bouncing about and dropping into a spinning gear.
 
I am totally dependent on the pictures you post. I see a side cover on the left hand side but no idea what you could access through it. You tell me. Is the top cover I see right in front of the dipstick part of the clutch housing. The clutch housing will attach directly to the engine. The next break or bolted together housing would be the start of the transmission.
 
Hi Winston, I hadn't spotted that side cover on the left hand side. I will remove it tonight and see if it gives any better access. cheers
 
Back to the workshop tonight and followed Winston's advice about the small access plate on the left hand side of the tractor and there were the last two sheared off bolts sitting in the left hand side of the sump. Now I can start work on the rebuild.

38451_3255af350e6f91a2d21a6d503667c71d.jpg
 
The first of the new gaskets made for the small access plate which has now been refitted. Is there any easy way to remove the old gasket residue that is on the main castings or is it just a case of working away with a scraper ?

38451_d46e9a1bbdbc6762d21522c6d7e34477.jpg
 
The next major job, after I have scrapped all the residue off from the old gasket, is to remount the two axles. The gasket paper that I have got is fairly soft and approx 1mm thick. Would you recommend using an RTV silicone on both sides or just fit dry ?
 
I am now starting to put things back together again. Diff if is back in and I have just refitted the left rear axle ( seen as if you were seated on the tractor )Now a question. Everything feels good, everything turns freely when put in to neutral, but when I turn the ring gear by hand the pinion gear turns but the axle at the point were the wheel does not turn. This will only turn if I engage what I think is the diff lock. Is that correct ( maybe I am looking at it the wrong way round and I am actually disengaging the diff lock when sliding over the small round wheel that has the points that lock into the gear ? ) should both rear wheels be driven all the time, have I missed something ?

38451_1fd740b6e0094cdd4a77f6c18dde803b.jpg
 
If I am understanding correctly then yes, that is normal. If you were to look at the splines on the right hand side of the differential you should see them turning. Least resistance will turn.

When you gently rotate the ring gear back and forth you should notice a few thousands backlash between it and the pinion gear. Do you have that?
 
Good morning Winston. Yes I do have just a tiny bit of play when I turn the Pinion gear in each direction before it starts turning the ring gear. Both axles are now back on and the diff lock mechanism refitted. Was a real pain trying to compress that spring. One thing I did miss and that was when I removed both axles I didn't drain the oil out of them through the drain plugs, that made a mess when I lifted them up for refitting.

38451_237f24fcbcec7bbff11c6779f1c3ad2a.jpg
 
All assembled now with tin work back on as final job. This was made a lot easier as I bought a load of new bolts that were exactly the right size so no messing about using old rusty bolts. Job was finally completed for less than $150 as there was no damage internally apart form the bolts on the diff being shredded ( most expensive thing was the oil for the gearbox at $90 ! ) Big thanks to Winston for his guidance at some crucial times during the tear-down and rebuild. Tractor now drives smoothly on all four wheels !
 
Hi Norm. the drive shaft that I am using slides in and out of itself and with the new ORC on just means that I don't have to pull it out quite so far. I assume that this will be ok ?
 
Hi Norm, ok I understand know. The shaft looks like it all fits ok when the bush hog is sitting on the ground but as you lift it the shaft needs to be able to reduce in length and if to long, Bang !
 
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