Immobilizing problem with hst DX29

   / Immobilizing problem with hst DX29 #1  

daTeacha

Veteran Member
Joined
Oct 27, 2005
Messages
2,463
Location
Funk, Ohio
I guess this fits here since my tractor is basically new. It could have been a major problem had it occurred anywhere other than where it did, and might help someone trying to decide between hydro and gear drive.

I had about 7 hours on my new DX29, was using it near my shop to move some firewood to be, basically a big pile of overly long wood my FIL brought over a while back. The tractor had been working fine. It's an HST, which was something I wasn't wanting at first, but decided on after driving it.

Like I said, I was right by the shop, actually within arms reach of it from the seat. I was moving some firewood with the loader when suddenly hydraulic fluid started squirting out near the loader quick connects. I shut it down, could see nothing wrong, but everything was coated in HyTran Ultra. When I restarted it, the flood was there immediately, even without using the loader controls. I had a busy evening with school stuff ahead and had to start getting ready, so went in to call the dealer and tell them about the problem. The tractor was going nowhere, but fortunately was sitting in my yard. Had it been out in a field somewhere, I would have been looking at a good walk back to the house or whatever.

Saturday morning, I got a chance to look more carefully at it. I wiped everything down, started it, shut it down immediately, and climbed down to see what I could see. The oil was coming from the bottom of the non-steering side of the hydraulic pump. Everything but the steering depends on the pressure in that line and it was leaking like a garden hose right at the pump. I called the dealer and told them I found where the problem was. They were going to send a guy out if I couldn't find it and if they could free someone up on a Saturday morning. Remember now, we're talking about 7 hours or so on the machine.

The service manager says he would check into what was what at that place on the tractor and call me back. He did, about 15 or 20 minutes later, saying it was an O ring, not a gasket, but they did not have that part numbered O ring in stock. However, they had drawers and drawers of O rings and probably had it, but under a different part number or from a different manufacturer. So, I took the line completely off the tractor and drove the 20 miles to the dealer.

While taking it off, I noticed that the assembly was under slight tension from misalignment. The line in question is L shaped, and the long leg of the L seemed like it should have been about 3/32 inch longer. I asked them about it, and they didn't seem too concerned, allowing that the bolts would make up for it.

Anyways, I got there, gave him the line with one good O ring and the bad one. A while later he comes back from the parts room with 4 new rings. They gave me a free hat and a free gallon of HyTran Ultra to replace what had spewed out on the ground. I figure I saved them two 40 mile round trips plus the time for the tech on the truck to come out, diagnose it, go back and get an O ring, and then fix it. I spent about 1/2 hour messing around getting the line back on since some of the bolts are not readily reached, it was on gravel and tree roots, and I had to work around the front tire, but it went okay. I needed about half the gallon to bring the oil level back up to full, and the hat doesn't fit my big head -- well, it does, but it makes me look like a pin head.
/forums/images/graemlins/smirk.gif
So, when considering gear vs. HST, consider that if this was gear tractor it would have at least have been able to move. If I was out far from the shop, I would have been stuck with this one. With a gear machine, I could have driven home in reverse, dragging the bucket on the ground, but at least I would have gotten it home.

I think if I was still shopping, knowing of this incident would make me stick with gears. Granted, it was apparently a fluke of someone getting the O ring crimped when putting the thing together, but the line not fitting exactly could be a contributing factor also. I have no idea why the ring didn't blow out when I had the bucket full of crushed limestone two days prior. There was no load on the loader when it let go. The fact that the dealer seemed to think that was normal was unsettling to me. I asked about shimming it, and he said not to since the other O ring would then have no seat.
 
   / Immobilizing problem with hst DX29 #2  
Rich, I agree with everything you said except that you would have been able to drive a gear tractor. This is the main hydraulic pump and has nothing to do with the hydrostatic transmission. The hydro pulls fluid directly from the reservoir. The main pump on the engine just supplies fluid for the 3PH and the FEL (and remotes if you have them). If it had been a gear tractor, you would have the same leak if I understand your description properly.

Glad you got it fixed, even if you did have to be your own mechanic. /forums/images/graemlins/cool.gif You just never know what may have been missed at the factory. It's a shame, but happens a lot. /forums/images/graemlins/frown.gif
 
   / Immobilizing problem with hst DX29
  • Thread Starter
#3  
Oh! Glad to hear that I would have been able to drive it then. I thought this pump ran the HST also, but on second thought, I guess it wouldn't. It does draw fluid from the same reservoir, though, doesn't it? I presumed so when I topped off the fluid. Or am I running low on fluid now in some other area that I don't know about?

I added 1/2 gallon to the tranny filler neck after it had leaked for maybe 5 real seconds, if that. Based on that, how far do you think I could have gone before running the HST out of fluid? I'm guessing not very far.
 
   / Immobilizing problem with hst DX29 #4  
</font><font color="blue" class="small">( added 1/2 gallon to the tranny filler neck after it had leaked for maybe 5 real seconds, if that. Based on that, how far do you think I could have gone before running the HST out of fluid? I'm guessing not very far. )</font>

You could probably have run the level in the reservoir down to about 2-3 gallons before you'd notice any problems if you stayed on completely level ground. The problem is that once you start having HST transmission cavitation, you are also having main pump cavitation too. If one pump burns up, you'll probably have both with damage. /forums/images/graemlins/tongue.gif With a gear tractor, you'd just burn up the main hydraulic and your gearbox would run dry for the transmission. You did the right thing by shutting down and getting the problem fixed like you did. I'm sure your dealer was very pleased that you shut it down too. /forums/images/graemlins/smile.gif

BTW: The hydrostatic transmission is really two pumps: 1) a low pressure charge pump (normally a rotary pump) that pulls fluid from the reservoir, routes it thru the cooler and filter, and supplies fluid under pressure to the input side to your main HST pump, 2) the main HST pump is a variable displacement piston pump supplying high pressure to the HST motor. The charge pump just makes darn sure the main pump never runs out of fluid. With the close tolerances on a piston pump, it can overheat and self-destruct very quickly when it starts to cavitate. Luckily, most of us with HST transmissions know to shut-er-down when the fluid runs low. /forums/images/graemlins/shocked.gif
 
   / Immobilizing problem with hst DX29
  • Thread Starter
#5  
Or in this case runs out (onto the ground) /forums/images/graemlins/laugh.gif
 

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