4WD Repair Jinma 284

[3RRL]

Hi guys,
Thank you for your approval on the repair.
It was quick and dirty but all got done in one afternoon.
Tom ...
There is no lube that gets in there other than the grease I packed during re-assembly.
Thanks,
Rob-

 

[rtdiggr]

Great job!!!!!! Hey Rob maybe you should start writing shop manuals in your spare time.

Shane

 

[Brunswick]

Thats pretty amazing stuff you did there. Nice shop btw. I can only hope my garage looks like that some day. What is equally impressive is that you say you got it all done in one afternoon????? It took me 3 days to rebuild the pump on my ride on mower....lol.

Anyway is this a worthwhile mod for owners of these tractors to do before the 4wd fails like yours did? I mean taking it apart and replacing the bearings with dowls would have to be easier than re-machining the whole darn thing after it fails.

 

[3RRL]

Hi Shane and Brunswick, thanks...
I made this repair because of the failure in that area.
I would be afraid to recommend to everyone to make the switch from the ball bearings to the dowels like I did because, even though it is working excellently, it is not OEM and for those who have dealers and warranties it might interfere by violating it.

However, if you think about that connection and what the purpose of those OEM ball bearings is, it is to transmit power from one shaft to another. Like I said earlier in the thread, there really is no pivoting of the joint like a true CV joint may have to do. Using dowels, the working contact area between the ball and spline is increased...at least that is of my opinion. And that's why I think it's a better condition. But that's also why I hesitate to tell y'all to go out there and switch it out. Then there's always the other side which says, "Now that THAT's a stronger connection, where is the NEW weakest point?" There are always negatives to think about. So I say, use your own reasoning and make a decision based on that.

On the other hand, although I haven't done it yet, I still plan to switch out the front balls to dowel pins.
It still seems to be the weak point reading other posts? There is also the clearances used in the machining of the OEM shaft and balls. Having seen first hand on both my Kama and the Jinma, sometimes the Chinese quality control leaves something to be desired. Loretta's front connection looks pristine to me, so I'm thinking replacing the balls with dowels would be of value. That front connection looks like it is fit better than the rear one which grooved over...perhaps from excessing clearance on the rear one there?

Instead of using 5/16" dowels, I'm thinking using 8mm x 10mm long dowels instead of 8mm balls would surely give you a better, stronger connection there if you were to switch over? If you can find them, I would recommend doing that. Although there is only .002" (2 thousands of an inch) difference between the 5/16" and 8mm dowels, one (the 8mm) is an OEM diameter and the other is a tiny bit smaller. I have only 5/16" dowels, so that's what is going in her front connection (for me). Perhaps after I install them I can report after say 50 hours of use. I don't know if I posted it or not, but she only had 185 hours on it when the rear connection failed. She now has 210 hrs and so far so good.
I better get to doing that front one pretty soon.

 

[Steve C]

Hi Shane and Brunswick, thanks...
I made this repair because of the failure in that area.
I would be afraid to recommend to everyone to make the switch from the ball bearings to the dowels like I did because, even though it is working excellently, it is not OEM and for those who have dealers and warranties it might interfere by violating it.

However, if you think about that connection and what the purpose of those OEM ball bearings is, it is to transmit power from one shaft to another. Like I said earlier in the thread, there really is no pivoting of the joint like a true CV joint may have to do. Using dowels, the working contact area between the ball and spline is increased...at least that is of my opinion. And that's why I think it's a better condition. But that's also why I hesitate to tell y'all to go out there and switch it out. Then there's always the other side which says, "Now that THAT's a stronger connection, where is the NEW weakest point?" There are always negatives to think about. So I say, use your own reasoning and make a decision based on that.

On the other hand, although I haven't done it yet, I still plan to switch out the front balls to dowel pins.
It still seems to be the weak point reading other posts? There is also the clearances used in the machining of the OEM shaft and balls. Having seen first hand on both my Kama and the Jinma, sometimes the Chinese quality control leaves something to be desired. Loretta's front connection looks pristine to me, so I'm thinking replacing the balls with dowels would be of value. That front connection looks like it is fit better than the rear one which grooved over...perhaps from excessing clearance on the rear one there?

Instead of using 5/16" dowels, I'm thinking using 8mm x 10mm long dowels instead of 8mm balls would surely give you a better, stronger connection there if you were to switch over? If you can find them, I would recommend doing that. Although there is only .002" (2 thousands of an inch) difference between the 5/16" and 8mm dowels, one (the 8mm) is an OEM diameter and the other is a tiny bit smaller. I have only 5/16" dowels, so that's what is going in her front connection (for me). Perhaps after I install them I can report after say 50 hours of use. I don't know if I posted it or not, but she only had 185 hours on it when the rear connection failed. She now has 210 hrs and so far so good.
I better get to doing that front one pretty soon.

Great information. A line contact is sure to last much longer than the point contact that the balls have. Using a slightly undersized dowel shouldn't hurt anything. It will just skew the force lines so they are trying to compress the inner shaft a little and trying to expand the outer coupling little, but since these forces are spread over a much larger area it is probably way better than the origional design. I am going to convert mine as soon as I get the time. It is a great improvement over the origional.

 

[Brunswick]

Sound advice. Im going to keep an eye on this thread for future reference. Given all the detail you put in here along with the pics its a better how to than most reference / maintenance manuals ive seen.

Thanks again,
Brunswick

 

[Diamondpilot]

You will find way better info here and on a few other sites from users like Rob. These guys know machinery and fix it right, and usually better, the first time.

Chris

 

[Pirate]

I think that clip that holds in the balls is also a problem. I replaced my stock clip with an e clip. Seems to be holding up real good. Moved around 35 tons of gravel and many hours later, all 4wd. The clip is holding good.

 

[Johnny P]

Rob,

Excellent piece of engineering. I am about to replace my drive shaft after having the tractor apart to replace the crank. I think I have it worked out especially having viewed you photographs. Unfortunately I didn't make note or take photographs of the drive shaft assembly when I dismantled it. It is now some 12 weeks since I did this and my memory is failing me on this one. Is there any chance of reproducing the full exploded view(s) of the transfer case/drive shaft/front axle setup.

Thanks Johnny P

 

[3RRL]

Rob,

Excellent piece of engineering. I am about to replace my drive shaft after having the tractor apart to replace the crank. I think I have it worked out especially having viewed you photographs. Unfortunately I didn't make note or take photographs of the drive shaft assembly when I dismantled it. It is now some 12 weeks since I did this and my memory is failing me on this one. Is there any chance of reproducing the full exploded view(s) of the transfer case/drive shaft/front axle setup.

Thanks Johnny P

Hi Johnny,
Unfortunately I don't have any photos of the assembly other than the photos I have.
Do you have the manual that has exploded views of that assembly? It too will show you the order. But maybe I can help (from memory).
The front driveshaft has a tubular cover on it. I think it's a 2 piece tube with a rubber cover where the 2 tubes go together...one inside the other. When the tubes are collapsed, that exposes the front and rear of the driveshaft. What I did for the front was install the star shape washer onto the shaft splines first. Then partially install the shaft into the front receptacle. The receptacle also has internal splines on it.



The reason for partial engagement is so you can then install the 6 balls into/between the shaft and receptacle splines. Then install the circlip retainer ring to keep the star shaped washer in position, up against the balls, so the balls don't fall out.

On the rear of the shaft, the female receptacle slides onto the shaft. But first you have to put the spring retainer washer on, then 2nd the spring, then 3rd the female receptacle. There is also a tubular dowel you have to insert into the shaft to keep the spring retainer from sliding toward the front. It also ends up providing a "push off" for that spring to stay onto the shaft coming out of your middle box. I did not tap that into the shaft until I got the rear part assembled (I think). That way you are not fighting spring pressure when assembling the rear part of the shaft.

OK, now you move the rear part of the driveshaft to the shaft sticking out of your middle box. Slide that star shaped washer onto the middle box shaft first. Then assemble the balls (like the front), so they are between the receptacle on the drive shaft and the splines on the middle box shaft. Then install the circlip retainer ring to keep the star washer up against the balls to keep them from falling out. Then move the spring retainer towards the rear to keep the whole assembly in position, and tap in that tubular dowel. I believe that's how I did it, but again, I'm going from memory.

Here is a partial assembly drawing of the rear driveshaft connection from my book.
Also a couple photos of the rear assembly with the balls (dowels in my case) inserted between the driveshaft receptacle and the middle box shaft.. Remember I actually took the shaft out of my middle box to repair it. So that shaft you see is that one, not the front driveshaft of course.



Man Johnny, I hope that helps some.
Plus, if I'm wrong where that tubular dowel goes, somebody please help.