Foton 404 PTO engagement - or not

[Chris D]

Hi all.
I've had this tractor since new in 2005 and worked out most of its peculiarities and fixed what needed fixing with spares always available from Affordable Tractors in the USA or Circle D here in Australia. I have the parts manuals for it. The latest issue is that the PTO is not engaging. These tractors have a two - stage clutch and two selectable PTO speeds. I'm confident that the two - stage clutch is working and sending drive to the gear selector which is beneath the three point linkage mechanism and immediately behind - and in - the final drive casing. It's"trying" to engage but won't. The input shaft (see photo) is turning when actuated. I understand that sometimes the roll pin fails. It hasn't on this occasion. I've not yet pulled it apart but will. I'm assuming that the dog clutch inside has lost some teeth or all of them. The parts manual is mildly helpful at showing how it works but it looks as though it shuttles to select either Low - Neutral - High PTO speed with the gears engaged the whole time. The dog clutch would seem to be the culprit.

I was hoping that one of you fine folk have better knowledge of what lies in this area. I'm expecting to pull the 3PL casting off to gain access to the final drive casing and see for myself. I'd appreciate any comments and any photographs of the internal PTO selector mechanism please. It will be helpful to me.
Many thanks and Merry Christmas to you all. Chris

 

[FordnMassey]

Hi,
Had any luck with this issue?

 

[Chris D]

Hi,
Had any luck with this issue?

No. Other priorities for in the way and I've yet to take it apart. I contacted a local supplier of parts for Jinma and Foton to see what spare PTO parts they ever sell and he said that most of the PTO problems occur in the actual (PTO) gearbox and not in the clutch. I'll get to pulling it apart and seeing for myself. I'm reasonably confident that the splines on the engagement collar are chewed down as a function of it not being fully engaged and suddenly coming under load and stripping. Or I might be wrong.... I'll post my findings in case someone else experiences this.

 

[Chris D]

Okay. I dismantled the appropriate parts of the tractor to get to the PTO mechanism and, like many things in life, found the problem and it was not what I thought it would be. First, to any home mechanics thinking of doing this job or even if you need to get into the final - drive area, after you have pulled all the covers etc off, give it good degrease and wash before taking it apart. Also try to make sure you have a copy of the Parts Catalog to suit your model. In my case, the catalog covers a number of models and there are differences in the parts and the diagrams. But it is helpful. Drain the oil first and be ready for a big volume of oil to come out; ~ 27 litres in fact. The drain bung is quite large and has a magnet on it. Likewise, the hydraulics / 3 PL assembly need to be drained - 12 litres for a 404 - and the pipe fittings that are removed should be covered - plastic bags work well. To remove this it requires an 18 mm socket and the bolts are tight so don't attempt it unless you have the correct size. 3/4 inch fits sort of. Don't try it. Once the bolts are undone, the whole 3 PL assembly can be lifted clear. There are no gaskets used on any of these faces - just silicone.

The 3PL assembly is heavy. Really heavy! Minimum of two people or preferably a chain hoist or similar is needed. Once it's off, you can see the final drive gears and the PTO drive gears. And, in my case, I could see why the PTO was not engaging. The cast fork that selects either 540 RPM or 1000 RPM, was cracked - see photo. Fortunately, it had remained roughly in place and not caused any more damage. To remove the selector fork requires removing the drive gears (top shaft) which sit on two very substantial roller bearings held in place by circlips. Removing this shaft through the rear cover took some doing in my case. It'd been there since 2005 or earlier and needed a combination of pulling and some hitting with a drift. But it did finally come apart and allowed me to remove the selector fork. The gears, splines and dog clutches all seemed in good working order. The photos don't show it very well but the general condition inside the transmission is pretty good. The oil was not burned (use a good appropriate oil made for these wet - brake final drives and you'll get no brake squeals) and there were no "big bits of metal" on the magnet. The bearings are readily available 6306N and 6205 roller bearings with or without circlip grooves. I'll put the new ones back with some anti seize on the surfaces!

I also found the PTO drive outer shaft seal had been badly fitted See photo) from day one but, fortunately, there are two of them side by side so the leaking had been minimal. The only other thing that was harder than it looked, was removing the split pin and spring from the selector fork. The spring maintains pressure on the ball on the selector rail and it is a substantial spring pressure. For any of us that have had that dreaded experience of these little steel balls falling into the base of a transmission/gearbox, in this case the ball is safely retained in the selector fork. Nice one Chinese engineers.

So, I'll order the new bits, wire brush the bolts, clean the cavities and reassemble. Like most things on these little Chinese tractors, they are massively over - engineered and very simply designed. Tolerances are all over the place and I found no shims and all straight cut gears meaning very little end - loading. They do make a bit of noise when operating however but that's to be expected. But, overall, I maintain my respect for them. They are cheap and made to be maintained and fixed with little complexity and with few special tools. In these days of "right to service" issues and special tools that lie across automotive and agricutural equipment, it's kind of nice to still have things that can be repaired with relatively low skills and a farmer's tool kit.

As to why this selector fork failed, I'd suggest the operator (me...) might have had some input to it. My caution to all such operators is to be a bit gentle when selecting. Sort of feel it into gear rather than wrench it. You know what I mean....

 

[FordnMassey]

Hi,

Interesting problem. I would suspect that the metal in that casting wasn't up to the task. Try snapping the broken one again as a test. We can soft cast metals from China Chiranium.

Nice explanation you did. It will be a help for other people.

 

[Chris D]

Hi,

Interesting problem. I would suspect that the metal in that casting wasn't up to the task. Try snapping the broken one again as a test. We can soft cast metals from China Chiranium.

Nice explanation you did. It will be a help for other people.

Thanks for your comments. I agree that the casting looks doubtful and the replacement, when I get it, will probably not be much better. At around $100 I did wonder as to whether I fabricate one from mild steel and I might still do that if the replacement casting looks doubtful. The design of the cast one throws a fair load onto about where it broke so a few webs or gussets there would be helpful. Looking in that gear case reminded me of looking in old Fordson's and Inter's built in the 1940's and 50's. Pretty simple and lots of metal. Crude and simple. Contrast that with my recollection of old MF 65 final drives. They were early adopters of planetary drives when most used bull gears on final drives. They were so well made and took a lot of abuse. Take care.

 

[philtyler]

Okay. I dismantled the appropriate parts of the tractor to get to the PTO mechanism and, like many things in life, found the problem and it was not what I thought it would be. First, to any home mechanics thinking of doing this job or even if you need to get into the final - drive area, after you have pulled all the covers etc off, give it good degrease and wash before taking it apart. Also try to make sure you have a copy of the Parts Catalog to suit your model. In my case, the catalog covers a number of models and there are differences in the parts and the diagrams. But it is helpful. Drain the oil first and be ready for a big volume of oil to come out; ~ 27 litres in fact. The drain bung is quite large and has a magnet on it. Likewise, the hydraulics / 3 PL assembly need to be drained - 12 litres for a 404 - and the pipe fittings that are removed should be covered - plastic bags work well. To remove this it requires an 18 mm socket and the bolts are tight so don't attempt it unless you have the correct size. 3/4 inch fits sort of. Don't try it. Once the bolts are undone, the whole 3 PL assembly can be lifted clear. There are no gaskets used on any of these faces - just silicone.

The 3PL assembly is heavy. Really heavy! Minimum of two people or preferably a chain hoist or similar is needed. Once it's off, you can see the final drive gears and the PTO drive gears. And, in my case, I could see why the PTO was not engaging. The cast fork that selects either 540 RPM or 1000 RPM, was cracked - see photo. Fortunately, it had remained roughly in place and not caused any more damage. To remove the selector fork requires removing the drive gears (top shaft) which sit on two very substantial roller bearings held in place by circlips. Removing this shaft through the rear cover took some doing in my case. It'd been there since 2005 or earlier and needed a combination of pulling and some hitting with a drift. But it did finally come apart and allowed me to remove the selector fork. The gears, splines and dog clutches all seemed in good working order. The photos don't show it very well but the general condition inside the transmission is pretty good. The oil was not burned (use a good appropriate oil made for these wet - brake final drives and you'll get no brake squeals) and there were no "big bits of metal" on the magnet. The bearings are readily available 6306N and 6205 roller bearings with or without circlip grooves. I'll put the new ones back with some anti seize on the surfaces!

I also found the PTO drive outer shaft seal had been badly fitted See photo) from day one but, fortunately, there are two of them side by side so the leaking had been minimal. The only other thing that was harder than it looked, was removing the split pin and spring from the selector fork. The spring maintains pressure on the ball on the selector rail and it is a substantial spring pressure. For any of us that have had that dreaded experience of these little steel balls falling into the base of a transmission/gearbox, in this case the ball is safely retained in the selector fork. Nice one Chinese engineers.

So, I'll order the new bits, wire brush the bolts, clean the cavities and reassemble. Like most things on these little Chinese tractors, they are massively over - engineered and very simply designed. Tolerances are all over the place and I found no shims and all straight cut gears meaning very little end - loading. They do make a bit of noise when operating however but that's to be expected. But, overall, I maintain my respect for them. They are cheap and made to be maintained and fixed with little complexity and with few special tools. In these days of "right to service" issues and special tools that lie across automotive and agricutural equipment, it's kind of nice to still have things that can be repaired with relatively low skills and a farmer's tool kit.

As to why this selector fork failed, I'd suggest the operator (me...) might have had some input to it. My caution to all such operators is to be a bit gentle when selecting. Sort of feel it into gear rather than wrench it. You know what I mean....

Thorough feedback. I have had the odd problem with mine, and as with you, if you can do a few things yourself you can literally save $$thousands.

 

[Chris D]

So it's all back together and working. Not overly complex but the bearings and counter shaft take a bit of getting into the right place so the circlips go into place. The bearings for mine were overly tight on the shaft so I polished a little bit off. As I flagged when I pulled it apart, the 3PL assembly which sits atop the final drive and PTO drives is really heavy. With everything cleaned and the old oil drained from not only the main diff' case but also from the transfer case and from the base of each of the planetary gear housings - little drain plugs in all these places - it's time to put the 3PL housing back. The photo attached shows how we did it with the aid of a block and tackle. It is conveniently swung from the ROPS frame at the top and with a sling to the 3PL arms at the bottom. Just needed a little bit of balance from my helper and it could be eased back into place. As I have said before, there's no gaskets in this area so any good gasket maker, RTV or the like will seal up the joint faces. And, if you are contemplating doing anything at this end of these little tractors, go and buy an 18mm socket if you don't have one; there's a lot of 18mm bolts used. Finally, the oil for this area is used by the PTO gears, differential, gearbox, transfer case and the wet disk brakes. As such it should be an Agritrans type oil suitable for wet disk brakes and will have an anti squark additive. 20W-30 (80W) will do it. The 404 takes 27 litres and I caution you, it needs 25 to 27 litres just to appear on the dipstick.

Best regards
Chris

 

[Gregster613]

Good well detailed write up! Glad you got it fixed and all back together.