Typically, simply changing the oil will bring these back to life.
It happens because the oil degrades over time, slowly carbonizing from internal heat and pressure, and losing a lot of the oil additives that make oil behave.
At some point, the oil is so degraded that it begins to mix with air, creating a foam or froth. When that happens, hydraulic principals go right out the window and the transmission plays dead.
You may have to take the transaxle out of the chassis and turn it upside down to let the old oil empty out the fill/vent, but I can do that a lot easier than prying $500 plus out of my wallet.
81 ounces of synthetic 20 W 50 motor oil and you will be pleasantly surprised.

Here is a link that might be useful: 325-0750, 36488

Thanks Mownie,

Your answer seems to be the only avenue open.

That trans is no longer available from Hydro-gear and was a special configuration for Ariens (as near as i can discover).

Rebuild parts recommended by Service Rep add up to over $300.
No labor in that figure.

No one sells refurbs or wants to rebuild unit. To dicey for shops to take a chance.

Can't even find one at local Mower salvage yards.

So, I have a project for next week or I am off to buy another Ariens from HD.

I have pulled out the hydro and upon draining I only get between 2 and 3 quarts. Have to measure it. When I checked the level before draining it was 1.625" from top of case to top of oil.

I am not going to crack and rebuild as I feel that with my skill level I would end up with a $300 - 400 parts bill and a non functioning hydro.

Is there a way to drain even more oil without splitting the case?

What 20W50 synthetic is favored?

81 ounces is the specified capacity, so "between 2 & 3 quarts" is just about right.
Brand of oil to use? Pretty much up to you. You may have to settle for what you can find in your locale. I used Royal Purple brand at the recommendation of a couple of forum members here. Only place I found it in my part of the world was at Pep Boys auto center. Can't say it's any better than other well known brands.
You will need to "purge the air" from the transaxle before putting it back into service (maybe even before you can get all 81 oz. into it).

Generic purging procedure.
Place the "free wheeling" lever into free wheel mode (transmission will not drive this way).
Sit in seat and start engine with brake/clutch pedal down, and the trans lever in neutral.
With engine at idle RPM, let the brake/clutch pedal up.
Move the trans control lever to FULL FORWARD and hold it there for a minimum of 5 seconds.
Move the trans lever to FULL REVERSE and hold it there for a minimum of 5 seconds.
Repeat the Full F to Full R at least 3 times.
Stop the engine and move the free wheel control to the engaged position, make certain it fully engages.
If you have gotten the entire 81 oz. of oil into the transaxle, you are ready for service.
As oil questions tend to foster discussions, I have included a link to BITOG.

Here is a link that might be useful: BITOG

Mownie:
Thanks for the purging procedure. I had read that in several threads, but your's it quite easy to understand.

I did a rough measurement of how much oil was drained. It came to about 68 oz. I figure the other 14 oz is trapped even after draining for several hours and tilting it in various positions. I went ahead and put 68oz of Royal purple (20w50 from O'reillys") back in and it brought the fill level back 1.625". I hated to leave that oil in, but I could not find out how to drain it all out.

I am going to reinstall the rear and see if there is any improvement. Will update with results.

14 oz. out of 81 oz. isn't going to hurt the performance.
The additive package in the fresh oil will only be diluted a small precentage.
Let's see how your machine performs with new oil. If your work rejuvenates the tranny, change the oil again........in two or three YEARS.

HI I have been following the Q&A on the hydro problem and fix in the form. I think I may have the same problem my self. I have a ariens seiara 1440H 10 + years old this is the first time it gave me trouble. I was wondering if one could drill a drain hole and tap it for a say 1/4 pipe plug. Seems to me it would save a lot of time taking out and reinstall the hydor unit. On mine the vent hose comes up behind the fuel tank under the seat area so refilling can be done with unit in the frame.Before some one says what about the metal bits from drilling and taping the drilling stuff comes out with the oil and the taping bits could be contained by putting some grease on the tap once the plug is in place future changes would be a breeze compared to removing the unit.Another benifit would be the oil drains faster as it is not air locked trying to come out the same hole as the air going in.I was looking at the area under the axel ring gear area. A bit to one side as not to nick the gear for a possable place to add the hole.Has any one had one apart who may have a better idea where to put a drain hole as not to damage any thing. just thinking out loud Fred

I am not sure how thick the metal is on the bottom of the casing. So getting a plug to hold is my main concern. It is probably doable, but would need some careful research before carving away.

I did have the following thought on a possibly quicker way to do this. The back plate below the seat is held on by 4 bolts. If they are removed along with the back plate, then the entire tractor could be hoisted in the air with a comealong or chainfall and tilted back to drain the entire unit. Sort of like bleeding a chicken. Then the unit could be easily refilled and the backplate reattached.

I did not get all the oil out, but I am guessing there is an internal chamber that is trapping it. Maybe if I had let it drain overnight????? The 62oz's that drained out, came out quickly.

As it stands right now, I took off the deck and the drive belt to check everything under the tractor, but that really is not needed to pull the rear. I dropped the rear, but left the control rods attached so that I would not have to , hopefully, readjust anything. I should be so lucky.

It only took me a couple of hours to reinstall the unit. If I had to do it again, it will be a much quicker turnaround.

I have been thinking about trying to locate a burned unit from the local Ariens shop to do an autopsy on. I will post that photo-link if it comes to pass. I was also thinking about running the drained oil through a coffee filter to see what was in there.

Here is a link that might be useful: Photos related to dropping transaxle.

The oil you were unable to recover was trapped in the hydraulic pump, the hydraulic motor, and the directional valve.

A least we're able to service these, I serviced a Tuff Torque 51A in a Scotts Deere yesterday, oil wasn't that bad but the screen was clogged. These are a pita since the unit needs to come out, 90 minutes for the round trip.

Well the mower is back together and I just got done with mowing the yard. 50 minutes in tall grass with the deck set at 4" in 85' heat. No problems and the unit has no stumbles or hesitations up and down the slope.

However, I am pretty sure that I did not have a hydro problem. Upon reattaching the drive belt, I found that the motor was loose and had dropped 2 out of four mounting bolts. I replaced the missing bolts and used red loctite to keep them in. I am guessing I had a loose belt slipping on the hydro. Oh well, At least I got to do some preventative maintenance on my hydro, sharpen my deck blades and clean things up in general. Plus the mower still works! Yay!!!!

To quote the Great One: And Away We Go.

{{gwi:343330}}

I did the trans oil change managed to get about 74 ozs in and that brought it up to 1.5 inch from vent hole top.I rotated it up on the front after the first 2 qts. I heard some air escape (glugging noise) then managed to get more in. After the reinstall and going through air purge process still no go.After some investigation I found I had put the spring on the wrong side of the brake bracket this also made the free wheel not work (I worked on it after a long day at work and forgot how it came apart and it was 3 days from take out to back in)Any how still not working right it would go then stop, but if I put the brake pedal down and released it it would go a few feet and stop again.After some more investigation. I found the drive belt came off the idler pully when I went to put it back on I found the pully had worn through on the top side ( plastic parts AH!! ) Probably the problem in the first place. I do not regret changing the oil as I found when I poured it back into the oil bottles it foamed a bit and air bubbles on top.I do begrudge the cost of the synthetic oil, hear in Canada It cost me $55 and change for 3 qts mobile 1 at CTC. only 20-50 synthetic I found was for motorcycles. I guess though I can not complain as the old unit 1996 must have a thousand or more hours on it three hours 30 weeks a year mowing grass with a 3 bucket bagger and a hundred trips hauling 10 cord of firewood big loads (yard trailer stacked about 300 lbs +) up hill from field behind house in the fall. Who said hydro trans were only good for flat lawns and light loads.

I have just been reading all the above forums about the Arien trans axel. I too have got one that will not move too good. I am in the process of draining the hydro fluid by way of a syringe. I have attached a small dripper line to the end of the syringe, started sucking the oil out, then removed the syringe to allow the oil to "self syphon" from the box. So far all going good. Might take alittle time, but atleast I can do other things at the same time. Will then use the syringe to refill the box. Will post again when this is done, and how it worked (hopfully) for me.

To follow up on my last posting, I got about 2lts of old oil from the box, then flushed out with about 100ml diesel oil, got that out the same way, it turned near black after mixing with the remains of old transmission oil. I then put back the 2lts of "Nunlon Automatic Transmission Fluid"
This is an Aussie product, but was advised by a hydrolics mate to put this, or similar product, into the box. Also to make sure it was a "Synthetic" not a Vegetable fluid.
Another hint was to check the 'Idler' pully that puts tention on the belt from motor to box. Mine had worn down so much that the belt was sitting right on the inside base of the pulley. With the new pulley, the belt sat up on the outer rim. With both the new auto fluid and the pulley, my ride-on now moves the same as when I got it.
Hope any of this works for others.
Thanks...The Bush-Man. (Central Australia)

I had a similar problem with my ariens 1540, Removing the unit took about an hour but doing it again i think I could do it in half an hour. After extensive research I ended up changing the oil to castrol GTX 20w-50 which castol recommends for the unit. A full synthetic oil would be better but I think hydrogear must have deemed that overkill and its probably just a waste of money. Don't put anything other than the correct grade, the manufacturer has tested this oil extensively. The main drive belt can wear too slipping in the pulley of the engine and hydrostatic transmission. V belts wear on the sides and the belt starts sitting deeper into the grove, there should be the a small gap under the bottom of the belt. When the belt wears to the bottom the sides of the belt stop gripping the pulley and it slips instead of gripping. Also the belt should be a heavy duty item, which is kevlar corded with a kevlar wrap so it wont burn out on the slipping pulley of the engine when idling or braking. These belts are a little more expensive but last much longer than a standard belt, Ive just put a new Stens True Blue belt. 1/2x80 248-80 on. After watching rebuilds on several hydrostatics it seems like most of the internal wear is either in the pump or the motor assembly which are about $60 from hydrogear and could be changed by disassembling the unit which i may do eventually.

heres the cheat sheet I made for my mower with the 15hp briggs and stratton vanguard engine, hope this helps someone as i spend hours researching everything.

Model no:936023 Serial
No:000211 Sierra 1540H

Briggs and Stratton
15Hp model number 28Q777-0645E1

air filter no:496894S
or

oil filter: 492932S

rocker cover
gasket:272475S

Oil: 1.42 litres SAE 30
Oil Penrite

Plugs: Champion RC12YC Torque 15FT-POUNDS

Valve clearance :INLET
0.004” EXHAUST 0.006” TORQUE LOCK NUT-70 IN-LBS

Cover bolts-75 in-lbs

hydrogear 325-750
transmission requires 2.39546 litres of 20w-50 motor oil

Recomended hydrostatic Oils-:

castrol agri MP plus
20w-40,CASTROL
GTX 20W-50, CASTROL EDGE 10W-60 SN

Valvoline XLD premium 20w-50

Valvoline Maxlife
20w-50

Penrite :
Small
Engine Four Stroke 20W-50

hydrstatic Filter:44964

Main Drive Belt Part
No: Ariens 936018 or Generic Belt no:A78K

heres are some cross refference numbers for the belt:

Allis
Chalmers 1666801 and 7166801

AYP
120418X, 12493S, 5904H and 74278

Case
C14965, C22708, C27708, C29680 and C29878

Cub
Cadet 489399-R1, 754-3037 and 954-3037

Dayco
L480

Ford
235956 and 328891

Gates
6880

Gilson
200624 and 212261

Goodyear
84800

Jacobsen
328891

John
Deere M47766 and M73223

Lawn-Boy
705766

Noma
314572

Power
King 810080

Sears
124293X and 74278

Simplicity
1666801 and 1672135

Stens
248-080

Toro
105476, 106571 and 106751

MODEL 200000 HORIZONTAL SERIES

ENGINE SPECIFICATIONS

Armature Air Gap .010 - .014 in. (.25 - .36 mm)

Crankshaft End Play .002 - .028 in. (.05 - .71 mm)

Spark Plug Gap .030 in. (.76 mm)

Valve Clearance – Intake .004 - .006 in. (.10 - .15 mm)

Valve Clearance – Exhaust .004 - .006 in. (.10 - .15 mm)

FASTENER TORQUE SPECIFICATIONS TORQUE

Air Cleaner Base / Backplate 90 lb-in. (10 Nm)

Armature 30 lb-in. (3 Nm)

Blower Housing 90 lb-in. (10 Nm)

Bracket to Carburetor (Snow) 45 lb-in. (5 Nm)

Carburetor Bowl Screw / Solenoid 90 lb-in. (10 Nm)

Carburetor to Cylinder Head 85 lb-in. (10 Nm)

Connecting Rod 100 lb-in. (11 Nm)

Control Bracket 100 lb-in. (11 Nm)

Control Panel Trim 40 lb-in. (5 Nm)

Crankcase Cover 100 lb-in. (11 Nm)

Cylinder Head 220 lb-in. (25 Nm)

Cylinder Shield 30 lb-in. (3 Nm)

Exhaust Manifold / Adapter 180 lb-in. (20 Nm)

Flywheel Nut 120 lb-ft. (160 Nm)

Flywheel Fan 140 lb-in. (16 Nm)

Flywheel Guard 30 lb-in. (3 Nm)

Fuel Tank 90 lb-in. (10 Nm)

Governor Lever Nut 40 lb-in. (5 Nm)

Muffler 180 lb-in. (20 Nm)

Muffler Support Bracket 125 lb-in. (14 Nm)

Oil Drain Cap – Front (Snow) 130 lb-in. (15 Nm)

Oil Drain Plug – Side 100 lb-in. (11 Nm)

Oil Fill Tube 30 lb-in. (3 Nm)

Rewind Starter 30 lb-in. (3 Nm)

Rocker Arm Stud 100 lb-in. (11 Nm)

Rocker Ball Set Screw or Nut 45 lb-in. (5 Nm)

Spark Plug 180 lb-in. (20 Nm)

Starter Cover 20 lb-in. (2 Nm)

Starter Motor 140 lb-in. (16 Nm)

Rocker Cover 75 lb-in. (8 Nm)

Snow Hood 40 lb-in. (5 Nm)

Snow Shield 50 lb-in. (6 Nm

-

I have a areins 1540 zoom zero turn mower the left rear axel is broke any ideas where I can get a used axel

garybullington

Do you mind me asking how long you have had this mower?