Hydrostatic drive lawn tractor help/advice

I know this may be off topic, but I also know that there are no smarter people in the world than those that read these pages. Since I am looking for information on a mechanical component, it may be of interest to some.

I recently bought a (new to me) Simplicity broadmood 1995 lawn mower in beautiful condition. The wife has given me much heat about it cause it will not climb a hill. I changed the oil in the hydro unit and it is more quiet, but still is slipping internally. It is a hydro gear 311-0750 unit. There is no drain so I sucked the fluid out and refilled. I can dis assemble anything and if I spot a problem, I can secure parts and repair. I can not afford to get a rebuilt unit. if there is anyone with experience with this type of unit, I would be grateful for any advice or guidance on how to repair this unit.

I have searched the net for days and have not found anything other than a parts list.

Does anyone here have advice on saving face with my family?

Thanks for any advice you may have.

What type drive, belt or shaft. Does the unit get hot? When you reverse back down the hill is it controlled or uncontrolled?

Stupid Questions

How is the motor connected to the hydro?

If belt drive is the belt tight?

How do you control the action...a single lever with variable speed both forward and reverse or more than one lever or pedal controls?

I have old Dines with 2 levers and Skag with 3 lever, adjustment of the controls change the amount of drive while a slipping belt would reduce the power and possibly not make a sound, it seems lawn mowers have dried out belts turning on smooth pulies at slower surface speed allowing for a slipping belt to not make any noise...don't ask how I know this...

Watch the input shaft on your motor, it should have a cooling fan on it, it shou dbe running constand speed, if it changes and the sound of the motor does not then the belt is slipping, if it does not change then the motor may be slipping.

I never have seen one fail, my dines is 30 years old and fine, and the manufacturer states a disassembly reduces the possibility of re-assembly...they do not suggest one be torn apart.

When climbing the hill..........

is it quiet, OR, is the trans whinning loudly, sounding like it is straining badly?

That model is hand controlled, we often see the plastic battery box base under
the battery installed backwards, this limits the linkage travel in the forward
direction. Be sure the level is moving full forward in the dash "slot".
If you have no external issue and the trans has a whine/growl under load
it likely has scoring on the piston block face (pump side) and or the housing where
they meet. This allows the oil to bypass and the output motor does
not get enough oil flow.
These also have a internal oil filter but we usually don't see them blocked.
Suggest if you've eliminated the external possibilities to just pull it apart,
there's not much to em and the damage is easy to see.
Good Luck
Dave

thanks for the advice

Dave P.

Your post shows a deep understanding of this unit. I found the battery box issue but it was not the real problem.

I can tell that the last owner tried the belt, there is a new belt and idler pulley, and it is not slipping.

I will begin the dis assembly. Can the face be re-ground?

I knew that one of the under appreciated mechanical geniuses here would have advice, thanks to everyone who made suggestions

Transmission

I realize that you said it is not slipping and has a new belt and idler pulley.

I had a rider with a similar issue. As it turns out there is a spring that holds tension on the idler pulley and the end of it was broken. It was under the frame and hard to locate. It had enough grip on the belt to drive it over level ground but would not pull up an incline.

Were you able to find a source of parts for the transmission? The one I was working one (forgot the name) did not offer service parts for it.

Another idea, if you are not successful in your repair efforts you might check around your local lawnmower dealer (Graveyard) as you might find a junk mower i.e blown engine with a good transmission.

Just a couple of thoughts. Wish you good luck in your repair efforts.

Let us know how your make out.

John

One more obvious thing on a Simplicity- the hydro's bypass valve (back end on my regent) is all the way in? This is the valve that allows the tractor to be pushed with the engine off...

Lucky7

Go on the web to Simplicity & Allis-Chalmers Garden Tractor, Inc. They can tell you all you need to know

it can be remachined. and does not need grinding equipment.

I did this a few years back to my neighbors simplicuty which started slipping just like you describe. I fixed it.

your system is slipping due to leakage between the barrel and port plate. wear increases the grooved area so that the oil pressure can seperate the barrel/port plate.

there is a balance of the oil pressure seperating via the grooves, and compressing via the piston area.

the cylinder can be re-faced by laying wet-or-dry on a surface plate and doing it by hand.
pay particular attention not to screw up the amount of surface area which is flat vs. purposely grooved. if needed work on the grooves with a dremel to maintain their origional coverage.

the port plate I re-milled smooth with a boring head i believe. it was somewhat recessed and made fly cutting with an ideally sized cutter difficuly.

It did not slip any more. It worked for about a year with no trouble. But in typical neighborly fashion no good deed goes unappreciated. I fixed it for free to be nice, then he sold it and bought a new tractor anyway. so I dont know how long it continued to work.

dsergison rules

dsergison,

I knew there was a way,

I often wonder if it is a gift to be able to fix this type of thing or a curse. It does not matter since I have to either fix it or it will remain broken.

I could get a replacement unit for 700.00 (if I had 700.00 to spend)

My wife and kids are watching the process, I hope to have a reliable lawn mower for several years to come.