Hydrostatic Drive

El Toro

Well-known Member
The tractor has been acting strange when trying to drive forward or reverse. Replaced oil filter and the oil looks clean. New filter didn't help. Oil level looks ok the 3/4 pipe elbow is full. Repair shop says there's no parts available. I bought it new in 1971. Engine has never built rebuilt. I did plow the garden this Fall. Anyone ever work on the hydrostatic? Hal
 
Look under the seat. There is a small shaft on top of hydro. If it is leaking there, then it is only a matter of time before it stops working.

I would give it a few weeks to burp it and get air out. Next, I would try to use thicker oil instead of what is recommended.

I have no experience tearing them apart. I am sure if there are seals to be replaced, then someone somewhere will have seals for it.

Other than that, I would look for a used one. There might be a few in a junkyard I visit here in Mi.
 
The repair shop told me to jack up the rear wheels
and put the control lever in the forward position.
Run the engine at 1/2 throttle. I did this didn't seem to help much. Which is the hydraulic pump? It may need rebuilding. The hydraulic lift works ok. Hal
 
Hi Hal, I put a tee next to the elbow, tee is pointing up, put a stand pipe about 6" long, it just fits next to the transmission, mine is a slight angle, I took a piece of 1/8" welding wire, welded it to the cap for a dipstick, we fill ours so the level is just below the axle.
I have taken apart all 3 of ours (2 1970's and a 1974) and put in new "O" rings and seals, found every thing over the counter.
The hydraulic pump ,motor is all in the casting, ours showed some wear inside, but seams to work ok
but notice some slippage going down hill. Jim
 
Any possibility the belt is worn or glazed, or a pulley is worn letting the belt ride too deep, the adjuster arm frozen and not tensioning?

I've had a slipping belt act exactly like a bad hydro.
 
Bull Dude, is this the the Monkey Ward/Gilson you often post about?

If so, it (HOPEFULLY) it has a bulletproof Sundstrand hydro.

Unless it has done something out of the ordinary and grenaded itself (as witnessed by lots of metal at the transaxle oil drain), about the worst that could have happened is a stuck or scored valve or broken spring in the pressure relief or charge pump area of the hydro.

That being said, I am not a Wards hydro GURU, but the Sundstand unit used is very similar to the unit DEERE used in the early 140's, which I have LOT of experience with.

(Unless they used a freak Eaton unit in that era???)
 
I called several repair shops and they said there's no parts available to repair it. I guess I shouldn't complain I bought it in 1971.
I'm going to drain the oil. Thanks, Hal
 
Hal,
You have been a member here for a long time so I am rather mystified by the lack of information in your post. Why have you not disclosed the year, make and model of the tractor you are working on or better yet..... the brand and model number of the hydro unit?

People are trying to help you with this problem but so far....you have kept them in the dark on the details.


Perhaps you are not aware of this but hydrostatic trans-axle units contain TWO pumps plus the drive motor that makes the gears and back wheels rotate.

The hydrostatic pump is a variable displacement pump that moves ZERO oil when the tractor is not moving. But if the Operator steps on a pedal or pulls a control lever, oil begins to flow to the hydraulic drive motor and the tractor then moves forward or reverse.

The 2nd pump is a fixed displacement pump that moves oil through the variable displacement pump constantly. This is done for two reasons. One - to keep cooler oil flowing into the variable displacement pump and TWO - to make sure the variable displacement pump is always full of oil and no air is present.

BTW.... no human can look at oil with the naked eye and determine if that oil is "clean". The good news is that your hydro is fitted with a filter but a filter does not negate the need to drain the hydro and refill it with NEW oil periodically.

The type of oil and the grade of oil is very important to hydrostatic drives. The first rule of thumb when working on such units is to drain them thoroughly and refill them with oil recommended by the hydro manufacturer. Engines in vehicles use oil too but those engines do not transmit their HP to the back wheels via that oil. Hydrostatic drives DO use the oil to transmit engine HP and that is why oil quality is so important.

So... how about finding the ID tag on the transaxle and reporting what it says?
 
The tractor was built by Gilson for Montgomery Ward. It's model No. 33048 and was built in 1971 and when I purchased it. Hal
 
OK Hal.... that's a good start but were you able to find an ID tag on the trans-axle? That would be a huge help.
 
Haven't found any tag. Not much room around that hydro. They recommend Type A oil. I don't think that's available. How about using multi-grade
synthetic engine oil? I have plenty of that for my Kohler generator. Hal
 
You should have no problem finding Type A fluid. This is the red coloured automatic transmission oil used in General Motors automatic transmissions and power steering units. Any auto parts store will have it such as NAPA, Pep Boys, TSC etc. I would stick with the Type A fluid and not add a new dimension to this problem by using an oil that is other than the approved one.


If you have owned this tractor since new, then the ID tag should still be on that hydro unit somewhere. As already mentioned, hydrostatic transmissions are made by several companies including Tuff Torq, Sunstrand, Eaton, HydroGear and Sperry/Rand.

Do you still have the original manuals for your tractor? Perhaps the maker of the hydro is shown there.
 
I have the parts manual there's no mention who made the hydro. We have a Pep Boys I will ask them about the Type A. Hal
 
Hi Hal, changing the oil and filter is good and hopefully that will get it going again, but if it doesn't I'd check the linkages I looked in my parts manual (1973) and there are a lot of joints etc many hydro need very little actual movement at the hydro input to change speed direction etc and many times worn joints in the linkage will cause problems, I ran into this with on a Ariens GT. I've not worked on a Gilson / Wards tractor with a hydro only the variable speed transaxles hope you get it going.
GB in MN
 
Were the variable speed tractors as good as the hydro's? No complaints on my tractor after 43 years. My oldest car is a 1981 Mercury Cougar my
late BIL told my wife's sister to get rid of it in 1985 with 15K miles. I drive it about once a month and is garage kept. Hal
 
Hal the variable drive tractor a built just like the hydros like a tank the variable drive assy is the weak link in that most of the time it never gets any maint. and wears badly the two I had were repairable and I had them rebuilt and they worked good simple nice way to get varying speeds, the good thing is if they can't be rebuilt (there are few if any good one out there and no new) one can just install a fixed pulley and the tractor is good to go as a 4 speed.
GB in MN
 
I used dexron, but it held just under one quart.
There were no metal particles in the old oil and not much oil drained. There's two 3/4 pipe plugs
one for filling and one for draining. After installing the oil and the right rear wheel I started the engine and it now has reverse and forward. Here are a few pictures of that hydro.
PS: Bottom picture shows the drain plug.
Hal
a171025.jpg

a171026.jpg

a171027.jpg

a171028.jpg

a171029.jpg
 
My advice would be to use the tractor and put about 10 more hours on it. Then drain the hydro again and refill it with fresh Dexron. Cost-wise.... this is peanuts vs what a hydro rebuild will run. The Dexron you just installed has a lot of detergents in it that dissipated, thanks to heat and age, from the old Dexron.

Fresh, clean oil on a regular basis is essential for hydraulics.

As for metal particles.... they were there. You just could not see them because they are microscopic in size. If you sent that oil out for analysis, you would be surprised by the report that came back.
 
Thanks Tom: I had planned on changing the oil again. The tractor has an hour meter and I very seldom use it unless I'm plowing snow and I'll haul several trailer loads of leaves out to the curb until they're all off. It will be 44 years old in Feb 2015. Hal
 
I found this rebuild on the internet. They said this was a Peerless / Tecumseh transaxle. I see
the word Tecumseh used in a Gilson parts manual. My tractor may have the Peerless. Hal
Untitled URL Link
 
I have a Bush Hog with a similar axle but the pump is different. The oil and filter is supposed to be changed every fifty to seventy five hours hours. There is a screen on the pickup just inside the drain plug. It appears your transmission is leaking
and may be the reason for the small amount drained out. Mine does take four quarts of A or Dexron. I always cut the filter apart to see what has been trapped. Hard to believe you had the tractor that long and never changed the oil ? The attached pictures are of another similar axel I bought for parts. I replaced mine several years ago when brass particles showed up in a cut open filter although it still worked fine. The hex socket plug is the fill and takes an elbow and pipe to use.
a171054.jpg

a171055.jpg
 
Peerless/Tecumseh built manual transmissions for many makes of lawn and garden tractors. I am not aware of that company ever building a hydrostatic transaxle.
 
I think the manual 4 speed transaxle in the Gilson / Wards were Peerless.
GB in MN
 
My memory says that A was for Ford and GM used something else that doesn't come to mind.....Delcotron or something like that. Ford stayed with it a long time before switching over to a similar oil to GMs; maybe the same spec'd oil. I used to know why but time has taken it's toll............not that any of this is important. The reason I know is I ran Fords at the time and had to ensure I got the right fluid.

Mark
 
I have a JD L110, about 16 hp with a hydro. One day I was coming from a muddy area and decided to clean off the front wheels. I'd turn the wheel fully to one side and goose it.

Something broke in the hydro. I took it apart and found the broken parts and I guess I got all the pieces. I found the mfgr. info on the thing and called them. They sent me the parts I needed direct with a "gimme hat" to boot. Interesting as the parts weren't but about $30.

I asked about oil and in the conversation I was told that the smaller units run dino oil and the larger get syn that they make. I said fine and don't remember what the oil was they recommended, 10W-30 I think, but I replaced it with syn and I am still running it after half a dozen years or so and haven't babied it.

I had never been in a hydro before but I jumped in and what appeared to be the fix was not all that complicated. Apparently I got everything back where it belonged as it still works like new. In short jump in and go for it!

Best I can do to help.

Mark
 

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