129 hydro issue

[cooperino]

So how do you know the plate is not worn allowing it to move beyond intended travel?

[J-Mech]

Originally Posted by cooperino

So how do you know the plate is not worn allowing it to move beyond intended travel?

LMFAO. Because it has a flat spot cast on it about 1.5" square that it hits. I've had a lot of hydro's apart. They don't wear. I've never had one apart that even had been hammered on. They don't wear that way. Besides, it would have to pound like 1/8" off the case before it would speed it up that much.

[Dart1917]

On the top speed issue Jon is correct. The Sundstrand manual specs show that at full forward the pump displacement equals motor displacement and you have a 1:1 ratio input to output. The output then goes into a 7:1 reduction gear which then goes into a 3.54 ring pinion gearset. So running through the numbers at 3600 input rpm we end up with an axle speed of 145 rpm. With a stock tire size at 23 inches that works out to 873 fpm or 9.92 mph. Without mods to increase pump output or some gearing changes that's what it is.

Now on the fast acceleration, if you are a 100% sure the external linkages are good then the only thing I can think of is the coil pins connecting the trunnion input shaft to the trunnion are loose letting the swashplate move farther than what the control is moving (have never seen this happen but anything is possible) . Hydros want to go full tilt naturally and the controls actually hold them back. Check the trunnion shaft at both ends to be sure they are pinned securely.

[J-Mech]

Originally Posted by Dart1917

Now on the fast acceleration, if you are a 100% sure the external linkages are good then the only thing I can think of is the coil pins connecting the trunnion input shaft to the trunnion are loose letting the swashplate move farther than what the control is moving (have never seen this happen but anything is possible) . Hydros want to go full tilt naturally and the controls actually hold them back. Check the trunnion shaft at both ends to be sure they are pinned securely.

Real quick then I have to run... gotta go to church.

I've had those coil pins break internally on the hydro. It (swashplate) still can't go any farther. When they break, you can't center the pump and you have no neutral. It won't ever stay in neutral when you put it there, and it won't go faster. You just can't ever get the tractor to hold still. You put it in neutral, then it starts backing up. You move the lever again, it stops, but then creeps forward. If they are broke.... you wouldn't be able to stop it.

[darkminion_17]

Originally Posted by J-Mech

LMFAO. Because it has a flat spot cast on it about 1.5" square that it hits. I've had a lot of hydro's apart. They don't wear. I've never had one apart that even had been hammered on. They don't wear that way. Besides, it would have to pound like 1/8" off the case before it would speed it up that much.

Got pics Jon?

[J-Mech]

Originally Posted by darkminion_17

Got pics Jon?

Not now, but I do have one out in the shop in pieces if I can find it.

[darkminion_17]

Originally Posted by J-Mech

Not now, but I do have one out in the shop in pieces if I can find it.

What a slacker.
I would just do as the others said and tighten up the hydro linkage, repair or replace as necessary.
BTW I had prolly 20 of those runaway tractors and as I mentioned above it took care of it.
This part seems to never wear out. Some have a machined plate that fit in the slipper area some do not.

[cooperino]

Originally Posted by darkminion_17

What a slacker.
I would just do as the others said and tighten up the hydro linkage, repair or replace as necessary.
BTW I had prolly 20 of those runaway tractors and as I mentioned above it took care of it.
This part seems to never wear out. Some have a machined plate that fit in the slipper area some do not.

It does not "run away" If I am understanding the term run away to me would mean you push lever say .75" to start moving forward while it stays and holds at .75" run away would mean it gets faster and faster even though you did not move the handle more.. Thats not what its doing. I can maintain speed.. When i push it forward really slowly I can control it at any speed. At some point in the forward lever it feels like its going way faster than it ever should, by time I push the lever all the way forward its going so fast that it feels out of control. The steering is tight enough and feels fine at speeds im use to from other tractors. The other part of the issue is when I move the lever forward any faster than barely moving it the tractor will either lift the front wheels off the ground "on pavement" or spin the tires like mad on grass. My other tractors will all spin the tires if I am really aggressive with them but quickly get traction and stop spinning. This is happening when I am working the lever gently. It does this with the throttle anywhere above say 40% of WOT and up.

[Dart1917]

Originally Posted by J-Mech

Real quick then I have to run... gotta go to church.

I've had those coil pins break internally on the hydro. It (swashplate) still can't go any farther. When they break, you can't center the pump and you have no neutral. It won't ever stay in neutral when you put it there, and it won't go faster. You just can't ever get the tractor to hold still. You put it in neutral, then it starts backing up. You move the lever again, it stops, but then creeps forward. If they are broke.... you wouldn't be able to stop it.

I knew it wouldn't go faster, was just thinking a loose swash plate would make for jerky control. If that's not the problem then I'm thinking Lew is on the right track about tightening up linkages. A little slop in each connection can add up to a lot at the far end.

[J-Mech]

Thanks for the pic Lew! Now I don't have to go dig it out. I was looking for engine parts the other day and found a hydro apart in a box.... I'd wondered where I'd put it. I've never organized the garage after I moved out of the shop.

I agree with loose linkages causing control issues, but he seems to think it has good control, it's just "fast". The left hand hydro tractors are just more "touchy" than the right hand ones.

Yes coop. If the spirol pin was cracked or broken it would be hard to control, but where you really notice it is when you try to put it in neutral. I've not ever had one break completely in half where you had no control. I'm sure it can happen.