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Anyone ever rebuild a hydrostat?

N

notjustair

Well-known Member
I use this mower to mow the barnyard, sooooo...

One of the hydrostats on my Deines zero turn mower is showing classic signs of having either a worn pump or drive motor (the other one isn't a whole lot better). Works fine for about 20 minutes and then struggles to get out of its own way, etc.

Has anyone ever rebuilt one of these? My understanding is that the pistons or the bores are wollered out enough that there is pressure loss. I haven't ever had one apart but I don't think I have anything to lose. They retail for about $800 new and I am sure I can gets parts from Eaton or an aftermarket supplier cheaper.
 
Does anyone offer reman hydro units for it ? My experience with large SP combine hydros, is that I could buy a reman unit, rebuilt by someone with the training, tools and skill, with a years warrenty on it, cheaper than I could buy the parts to attempt my first time amature job with questionable results and no warrenty.
 
The majority of the hydrostats used on the mowers are not rebuildable. The housings get worn and they are cheaper to just replaced with new.I have seen them bored and sleeved back to size but the cost is more than a new unit costs if the unit is available.
 
I've got a Hydro-Gear apart now. All I'm doing is replacing the broken axle, but while researching the part I found an online service manual that covers the rebuild. Nothing appears to be difficult, no special tools, parts are available and reasonable. Really simpler than I had envisioned.
 
Piston pumps and motors are pretty much identical in design and function. That being said, I have had to get a lot of the pumps rebuilt, and the advice given so far is pretty good.

For the larger units, rebuilds are the way to go. On the small ones you'd probably have more in a rebuild than in a new one.
 
A quick and cheap way to get a bit more time from your hydrostat that is worn and bypassing too much is to use a thicker oil than specified. I did that with a hydrostat swather and it's completed its 5th season since. Note that this isn't the same as rebuilding but it's a lot cheaper.
 
This may not be you situation but check belt tension. Have worked on several ztr's that owners said it would not pull good on one side after warmed up. Replaced belt if tension was not adjustable or adjusted tension by the manual.

Rodney 8)
 
This is the hydro in question (not my pic). Actually, it's simpler than this as it does not have the right angle drive. Just the front driven (fin side) and the back drive (gear to roller chain). It's a 35 year old mower and I have extras that are bad that I can tear apart to order pieces. I hate to spend 1200 bucks on a couple of new ones even though I use the mower hours a week and it mowed like new. Some old metal just isn't worth it!
a222305.jpg
 
The hydraulic shop I go to often to get hydraulic cylinders worked on is always working on ZTR's. The last one was working on had twin 25 hp engines on it. I asked him what ususally goes wrong with them. He said "PUMPS AND MOTORS, PUMPS AND MOTORS." I asked how long do they usually last? He said depends on how well they are taken care of, but usually 1000-3000 hrs.

Good luck.
 
My John Deere rider was like that after it was warm wouldn't go up small inclines. I replaced the 30w oil it called for with 20w50, that was three years ago still doing good. the hydros in the JD mowers are built by tufftorque. Jim
 
If my memory serves correctly I had one of them apart maybe 40 years ago. Nothing like a traditional hydrostat with a head, pistons, and swash plate. This had a fairly large diameter, but narrow rotor, with balls around the perimeter. I have no idea how it functions. The one I worked on just quit. A socket/allen head screw/plug had loosened and fallen out of a hole near the center of the rotor. This was on a New Holland/Ariens S-8 lawn tractor. The baby of the line. I think I saw the identical hydrostat in a small IH lawn tractor.
 
I have a brand new jd tranny ,, bought at auction ,, sold to po as brand new and never used,.you can have it for 50 bux and shipping ,,, I am in Louisville ky area
 
Industry wide that is called a throwaway unit. Nothing in there rebuildable, where the wear is going to be will not be replaceable. We do some of the large units that cost 2 grand or so. Problem with rebuilding hydros is by the time you replace everything that needs replacing and the labor you are right back to the cost of new. Easy to open oune up put a new plate in and make it go thru an auction or run for 30 days but for long life just about have to replace everything.
 
Same with the torque motor on my Terramite. No parts available. Replacement cost $800. Throw away.
 

Drain and replace with Amsoil straight weight 60 oil. May have to drain the mixture of old oil and new once and re-fill a 2nd time.
My LX188 quit moving on hills six years ago. It's been running since on the 60wt.
 
Call the Surplus Center for a catalog,the one I got in the mail this week has several hydros listed for ztr
 
I've got a Hydro-Gear apart right now too. The only thing I found wrong with it was the dirty and worn out oil. 15 years of mowing and snow plowing will do that I suppose. New filter and seal kit should be here this week.
 
Depending on your set up sometimes a pump will start to go and put metal through the hydrostat. Put a new hydro motor on and the bad pump throws more metal through the hydro ruining the new one. Watch for bad pump and metal in the oil. Flush well.
 
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