Opinions on hydro operation.

cubs-n-bxrs · #1 06-29-2013, 01:30 PM

I just nicely got this 1711 hydro put together that I acquired from Donovan in a trade. The hydro acts a little wierd and am looking for opinions. When you take off it's nice and smooth then it is like it hits passing gear and speeds up. Tunnel cover is off all linkages are in good shape and the trunion is in real nice shape so I have ruled out them possibilities. The trans was cleaned out and new fluid and filter. I myself am leaning toward a sticky relief valve. Whats everyones thoughts on the situation?

I have 6 different hydros and never had one act like that.

jimbob200521 · #2 06-29-2013, 02:07 PM

Does the hydro lever have any resistance when you go to accelerate or slow down? It could be something as simple tightening (or snugging, rather) the nut and bolt that holds the hydro lever on to add a little resistance to the lever. I'm not sure if how I said that makes sense or not. I'm sure someone will chime in and clear things up.

Edit: From the looks of the mower, you'll have to lift the hood, take off the drivers side (right) engine panel, and there should be a bolt that you can tighten to help the lever not drift. I had the same problem on mine and that solved it. Good luck!

Sam Mac · #3 06-29-2013, 02:17 PM

You may want to do some pressure checks on it. Does that have a ported pump on it?

cubs-n-bxrs · #4 06-29-2013, 02:49 PM

Lever is fine with plenty of resistance. Actually had to back the nut off 1/8th turn because it was extremely hard to move. Yes it has a ported pump Sam. Hydraulic lift lower seems smooth and trouble free. Gonna swap out the forward relief valve as it has started leaking.

J-Mech · #5 06-29-2013, 02:49 PM

As long as the lever itself isn't moving on its own, them I agree with Sam. If the lever is moving on it's own, then Jimbob is correct. And yes the 1711 has hydraulic lift.

J-Mech · #6 06-29-2013, 02:51 PM

Quote:

Originally Posted by cubs-n-bxrs

Lever is fine with plenty of resistance. Actually had to back the nut off 1/8th turn because it was extremely hard to move. Yes it has a ported pump Sam. Hydraulic lift lower seems smooth and trouble free. Gonna swap out the forward relief valve as it has started leaking.

You answered before I got mine posted..... Good idea to swap the valves. Make sure the trunion spring is ok. If it's weak, or missing the "caps" on the ends of it, that would make the hydro work like you are describing.

Sam Mac · #7 06-29-2013, 04:11 PM

Kelly see if the lift has any effect on it. I've seen some supers that when you hit the lift or even steering it changes speed. As far as I know it causes the charge pump pressure to increase and that gives the piston pump a boost in pressure.

ken6x6 · #8 06-29-2013, 06:40 PM

^^ my 782 does that, when you lift the mower deck wile moving and hold it, it speeds up. as soon as you let it go it returns back to the original speed.

J-Mech · #9 06-29-2013, 06:47 PM

Quote:

Originally Posted by Sam Mac

Kelly see if the lift has any effect on it. I've seen some supers that when you hit the lift or even steering it changes speed. As far as I know it causes the charge pump pressure to increase and that gives the piston pump a boost in pressure.

I don't follow Sam.... What are you getting at... Charge pump relief valve? Or weak charge pump?

Quote:

Originally Posted by ken6x6

^^ my 782 does that, when you lift the mower deck wile moving and hold it, it speeds up. as soon as you let it go it returns back to the original speed.

I really think that is normal.. Like Sam said, whenever there is a spike in pressure, well actually it would be flow, it's going to speed up the hydro. When you hold the hydraulic lever till the cylinder stops, then continue to hold it, there is no where for the oil to go. So, it has to go through the relief valve. Which, in turn, causes a spike in pressure that is feeding the hydro, thus speeding up how fast it runs.

Sam Mac · #10 06-29-2013, 07:43 PM

I think it's more of a worn piston pump and when you hold the lift lever and the ram is at the end of it stroke the pressure in the implement circuit builds and causes the pressure to the piston pump to increase. I'm not an expert in this so I could be completely out in left field. One of these days I need to study these things a bit more. Good thing most of this stuff is in the tech manuals.