Jinma 284 transmission jumps out of gear

[jlsteiner]

I have a Jinma 284 that Jumps out of hi-lo range, the shifter near the front top of the reansmission, can anyone give me an idea what to do to fix this short of tieing it in gear, especially bad in low range. I took the top off but was unable to get a feel for what to do.

 

[greg_g]

How many hours? I had a Yanmar that did the same thing, it was because the teeth on the range select gear had rounded off. But most Chinese tractors in America don't have enought hours under their belts to exhibit that kind of wear. If it's a low hour tractor, I suspect it's more likely a loose linkage.

I think the Hi/Lo selector is roll pinned to the vertical shaft, right? Then there's a lash up where a spring holds a steel ball into a hole that's related to the Hi or Lo range? Often those parts get dirty, and the ball doesn't seat properly in the hole. When that happens, it only takes a little feedback torque from the transmission to pop the ball into the wrong hole - taking the lever with it

If that's not the problem, c'mon back - we'll explore further.

//greg//

 

[jlsteiner]

Only has about 50 hours on it, it started jumping out of gear with in the first 20 hours. I will have to pull the top back off, to check but I could not see anything when I looked the last time. If I remember correctly the shifters that go down to the gears have the spring and ball on the inside, I think I would have to split the tractor to remove the rails to get to the springs. Perhaps if I take the top off and spray some PB blaster in and around the shifters It would help.

 

[Rich Waugh]

Bad idea - PB Blaster is not the sort of stuff you want inside a gear case. If you think something is gummed up, drain the gear oil and refill the transmission with diesel fuel. Drive it around for a half hour or an hour, using all the gears, then drain the diesel back out and refill with fresh gear oil. You should have done this when the tractor was new, unless the dealer did it, so it might be a real good idea to do it now. Ditto for the lifter assembly (hydraulics).

 

[RonMar]

In the case of the creeper gear, the rod is pinned in place and the shift fork slides on the rod. When you pull the creeper cover again, you will see the fork assembly with a notch in the top. The part of the control lever that is inside the top of the cover rests in this notch. There is a hole in the notch that will allow you to see the grooves that the ball and spring engage. Under that rod is the spring and ball that engage grooves in the rod that are supposed to hold the fork in the high and low position. You can look down into the hole to see if the hole is aligned with the grooves in the rod for the high and low position. IF you take a big screwdriver and wood block, you should be able to push/pry on the fork to shift it between high and low range(you may have to roll tractor a little to get gear teeth to align). Do this and observe how far the gears engage and wether the ball detent hole aligns with the rod grooves. If the fork will not move far enough to align the hole with the grooves, you need to figure out why.

IF the fork does move far enough to align the spring hole with the rod grooves, replace the top cover so the inside lever is in it's notch. Then shift the lever back and forth between the high and low position, pulling the cover after each shift to see how the fork position compares to how it was when you moved it with the screwdriver and block of wood... If it is not aligning the hole with the rod grooves using the lever, you need to find what is keeping the lever from moving the shift fork far enough.

Play with it a bit, you will see how simple it operates...

Here is a link to ranchhand supply's excellent technical photos. The top group of photos is for the transmission with the creeper gearbox, and most of the top row is of the creeper gearbox with cover removed.
Jinma Dealer, Wood Chipper , Compact Jinma Tractors

 

[greg_g]

I see Ron caught it. You said Hi/Lo, and I immediately thought range select. I missed the part where you said "near the front top". That would be the creeper gear select. But Ron got caught up like I did - talking hi/lo instead of creeper engage/disengage - so I'll take another stab at it.

Yes, there is a spring and ball arrangement involved. The outside creeper lever (51) is connected to an inside finger (43). That finger fits on top of a fork (4) that moves a sliding gear (1) back and forth on a rail (2). The position of the sliding gear on the rail determines whether the creeper is engaged or disengaged.

The fork has a hole in it, and the rail has two grooves in it. One groove relates to engaged, the other to disengaged. The ball/spring (5/6) fits inside the hole in the fork. Although I don't agree with the diagram; I'm pretty sure it's ball first, then spring. The ball then sets in one rail slot or the other, depending upon where you move the lever. Note also the rail roll pin (3). If that's missing or broken, the rail will not remain stationary. Rare, but possible - that would cause the rail to move with the lever, rather than the gear sliding on the rail. And if/when you find that anything is missing - especially that steel ball - find it before operating the tractor. I had one fall into my transfer case once, which involved not insignificant tractor downtime and repair costs.

//greg//

 

[ditech]

Hi Guys,
In reference to the diagram posted in Greg's post. The positioning of the detent spring and ball (5&6) is correct. The spring is installed before the ball. The spring and ball rest in a blind well in the shift fork and are captured in that well by the shift rail. I don't believe there is any way to inspect the spring or ball without removing the shift rail.

Ditech--

 

[RonMar]

Hi Guys,
In reference to the diagram posted in Greg's post. The positioning of the detent spring and ball (5&6) is correct. The spring is installed before the ball. The spring and ball rest in a blind well in the shift fork and are captured in that well by the shift rail. I don't believe there is any way to inspect the spring or ball without removing the shift rail.

Ditech--

+1, the spring is in the bottom, and the ball is pushed down on top of it with a punch, then the rail rod with the grooves is slid in over the compressed spring and ball. The top right hand pic in the link I posted shows the cast pocket where the spring and ball go fairly clearly... No way to inspect the spring and ball, unless you remove the fork from the rod. But the hole in the top does allow you to see if the fork is moving far enough to align the hole with the grooves.

 

[greg_g]

Ok, I think I get it now. The other spring and ball slide rails I've worked on detente from above or from the side. If I read you right, in this application the ball and spring install below the creeper rail. Thanks for the clarification

//greg/