My ZD series lawnmower is moving slower after a couple years. It moves at about half speed. Is this an indication that there are some leaky valves in the hydraulic system? The Engine runs fine, rpms stay high when in motion. What all should I replace to bring it back up to speed?
ZD series mower moves slower now
- Thread starter gslice
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How many hours do you have on it now? I have a ZD21 with 175 hours and it is just broke in and actually moves better than new. I use AW-32 mil spec hydraulic fluid rather than the super HHD kubota oil. You may have a heat issue causing a loss in viscosity together with wear causing an unexceptable clearance between your pistons and barrel GPM flow rate in one or both of your variable hydrostatic pumps. In other words you have too much case drain when hot creating the loss of fluid power. This translates to loss of speed and low power physically with the zero steers.
ronjhall
Super Star Member
May not be related. But my JD mower started moving slower. Found that bolt hold forward pedal had come loose. Pedal was bottoming out on frame which caused only about half speed.
Yea Ron thats a good point but his speed is directed by his steering arms and he has the spec for this adjustment in his operator manual. I hope I didn't scare him off with my hydraulics background. If he has a lot of hours on a Zero it stands to reason that "scar wear" in his variable hydrastatic pumps barrel to piston clearance will cause this machine to slow down long before total function loss calls for a remanufactured unit. When mine wears to this point I'll just pop a new unit in. I do know some professional lawn care guys with upwards of 3000 hours on ZD28-72p decks who have went this route
rather than rebuild components.
rather than rebuild components.
ronjhall
Super Star Member
Those ZTR's confuse me. 
SkyPup
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Our ZD-21 has 275 hours on it now and since we've only used Kubota's SuperUDT hydraulic fluids, we've never expericenced these kinds of problems.
It is truly amazing how smooth, quiet and responsive it is.
BTW, the kinematic viscosity of the Super UDT cannot be matched by any straight cut hydraulic oil, the flow rate of the SUDT is over 800% faster.
In fact, using any AW-32 straight stock is the reason you have such low flow and excessive heat problems and major repairs to begin with.
It is truly amazing how smooth, quiet and responsive it is.
BTW, the kinematic viscosity of the Super UDT cannot be matched by any straight cut hydraulic oil, the flow rate of the SUDT is over 800% faster.
In fact, using any AW-32 straight stock is the reason you have such low flow and excessive heat problems and major repairs to begin with.
JJT
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My ZD21 is 3 years old, with 150 hours and it mows as new.
curt1
Silver Member
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My ZD21 is two year's old and has over 400 hour's on it. This may not be your problem, but at about 350 hour's I noticed a loss of power in my left side steering. It had about half the speed of the right side. I fixed it by checking the linkage from the steering handle's to the hydro pump's. One of the nut's was loose allowing the linkage to be loose, resulting in what seemed to be a loss of power. Be sure to check the linkage and adjustment's. How many hour's do you have on your machine?
A machine which has been properly serviced and has low hour's should not have a hydro problem. But anything can happen. Maybe your's will be as simple to fix as mine was.
Curt
A machine which has been properly serviced and has low hour's should not have a hydro problem. But anything can happen. Maybe your's will be as simple to fix as mine was.
Curt
Hey Captain Kirk he's not using AW-32. He's probably using factory oil. I bought a crate tractor (wholesale) dry as a bone so I know for a fact all mine has ever seen is AW-32, except for bench testing at the X7 plant. 187 hours and running as strong as ever.
