Trouble with DK45SE HST Transmission

[Barj]

Hi,

I own a Kioti DK45SE HST and I'm having transmission problems. It started about 3 years ago out of the blue. I was about to drive up my lane and put it into high gear (something I did all the time) but this time it wouldn't move. Put the tractor down into medium and off it went. Slowly I discovered that the tractor had no power in high and the tasks it could normally do in medium had to be done in low. The tractor only had 320 hours on it (but out of warranty). I took it into my dealer. The transmission needed to come out (split) to check. They found nothing. I got the tractor back. It wasn't it's self but was at perhaps 80%. Slowly it got worse and once again the tractor had to go back to dealer. Once again transmission was split and nothing was found. It's limped along since then functioning well below it's capabilities and now it's hit that slide again. There's now 500 hrs on it and high gear is nearly useless. I've been dealing with this through my dealer and directly with Kioti but both have backed away offering no insight. Has anyone had or heard of this problem before?

Thanks

Barry

 

[k0ua]

Hi,

I own a Kioti DK45SE HST and I'm having transmission problems. It started about 3 years ago out of the blue. I was about to drive up my lane and put it into high gear (something I did all the time) but this time it wouldn't move. Put the tractor down into medium and off it went. Slowly I discovered that the tractor had no power in high and the tasks it could normally do in medium had to be done in low. The tractor only had 320 hours on it (but out of warranty). I took it into my dealer. The transmission needed to come out (split) to check. They found nothing. I got the tractor back. It wasn't it's self but was at perhaps 80%. Slowly it got worse and once again the tractor had to go back to dealer. Once again transmission was split and nothing was found. It's limped along since then functioning well below it's capabilities and now it's hit that slide again. There's now 500 hrs on it and high gear is nearly useless. I've been dealing with this through my dealer and directly with Kioti but both have backed away offering no insight. Has anyone had or heard of this problem before?

Thanks

Barry

I have heard of a Kubota with that problem. It turned out to be a relief pressure valve problem in the hydrostat. I would think the dealer could do pressure readings without splitting the tractor. Do you have a service manual? I am thinking your dealer doesn't have one. Nor the pressure gauge. I am thinking you need a new dealer..

 

[Alien]

Most transmissions I know have pressure check plugs where a guage can be plugged in. I agree with James.

 

[Barj]

I have heard of a Kubota with that problem. It turned out to be a relief pressure valve problem in the hydrostat. I would think the dealer could do pressure readings without splitting the tractor. Do you have a service manual? I am thinking your dealer doesn't have one. Nor the pressure gauge. I am thinking you need a new dealer..

Thanks for the advice. I do not have a service manual but will be getting one. Also, unsure whether relief pressure valve was ever checked so will look into it. I'll post an update.

Barry

 

[Alien]

Just occurred to me that others have had the problem because their rear hydraulic levers were not in the correct position. Hope you have it sorted.

 

[Barj]

Just occurred to me that others have had the problem because their rear hydraulic levers were not in the correct position. Hope you have it sorted.

Thanks for the response. Still sorting issue. Can you explain a little further. Do you mean they were left on causing a power drain (hydraulic) or simply installed wrong?

Thanks

Barry

 

[k0ua]

The hydrostatic transmission pump and the hydraulic remote pump are 2 different pumps. The accessory pump which is usually 2 stages is driven off of the camshaft of the engine and this pump is located up on the side of the engine and provides flow for the accessories like the loader, any rear remotes, and the 3 point lift. The second stage is usually directed to the power steering. The hydrostatic pump is much larger and is coupled to the crankshaft of the engine. These are separate systems, although some of the functions of the auxiliary pump do provide some function to the hydrostatic system in some models of tractors.

For instance the 265 psi charge pump function to the hydrostat is provided by the 2nd section of the auxiliary pump after passing thru the power steering section. Also the aux, pump can operate other functions like the 4wd hydraulic actuation and/or PTO hydraulic activation. The pressure in the main Hydrostatic pump is near 5000 psi. This high pressure then flows to the large hydraulic motor that drives the 3 speed gear transmission (3 ranges) that provide power to the final drive gears. This high pressure flow is controlled by the swash plate whose angle is et by the operator actuating foot pedals. In some models, like mine for instance that swash plate angle is actually set by a hydraulic servo under control of the pedals. Some models are controlled directly(mechanically) from the pedals. My point is in some models of tractors a loss of the accessory pump could prevent the hydrostatic system from working and some models not.

 

[ritcheyvs]

I have a gear tractor so no first hand experience on this.

But looking at a service manual for HST models, there appear to be simple HST pressure checks that can be done without disassembling anything. There are ports (under the left step, as I recall) Did your dealer do these checks? Those tests should tell if the charge pump function is OK, if HST pump function is OK and if the relief valves are OK. The problem may be as simple as a restriction in the charge flow (when were hydraulic filters last changed?) or a sticky relief valve. Do you notice a difference between forward and reverse? If so, it could just be the relief valve.

The HST concept is pretty simple: a variable displacement piston pump drives a hydraulic piston motor. That motor drives a conventional L-M-H gear transmission. The service manual has a fault isolation process for insufficient power,

 

[Barrettseq]

I had a customer with the same problem and it was the brake lever that went into the rear axle. He had no power in high and when you drove the tractor, kicked the H-M-L lever into neutral it would not roll at all. I got under the tractor, disconnected the brake pedal and noticed that the brake axle lever was froze up. I released the lever and drove the tractor again, dropped into neutral and it rolled just like it should. Take a look at that and let me know.

 

[jblackthorne]

Haven't worked on a tractor HST (yet), but I've done a few riding lawn mower HSTs. In those, the HST has two adjustable plates, one in the transmission pump (engine side) and another on the transmission motor (axle side). One plate is adjusted by the forward/reverse pedal, the other plate is adjusted by range selector. This F/R pedal causes the fluid to change direction of flow. Often these designs will utilize two different overflow values, one for forward and one for reverse. Because of this, many owners will notice a loss of power in one direction, while things seem normal in the other direction. Most often the forward directional value is the first to start failing. I've only seen a handful of cases where the reverse value started failing before, or at the same time, as forward. All those belonged to owners that were from areas with generally very hilly land, which may had contributed to the equalization in failure rates.

Usually (90% of the time) most failing valves will fail a 'spring length test' - where you simply measure the springs length (no compression), and if its not long enough, it fails. Only a few failing springs will pass the above test, and have to be compression tested to detect the failure.

Typically, if someone comes it with such a problem, and their machine has 500+ hours on it (less if they have very hilly lots - I ask). I won't even bother to check the springs and just replace all the values outright. Sense you have it apart anyway, right?! An entire set of values would likely be $200-300 (guessing, based on cost for the small ones I use) for your tractor, plus whatever labor is. I always replace them all at once - especially if one had a detectable failure. As it saves the guy another trip to the shop, 50-100 hours later, when the other direction starts failing.

You may want to check if a rebuild kit is available. These would normally include a complete set of overflow/bypass values, d-balls and/or needles, return springs and most importantly a full set of gaskets.