Small Engines (Lawn Mowers, etc.)/Snapper GT180H Series 4


M wrote at 2013-01-02 21:30:43
This very same thing happened on my series 4 snapper tractor with an Eaton 850 transaxle.

The system is very basic no valves only a main pump and 2 motors wich are mounted to the

axles that drive the wheels.  In the case described the operator presses forward and the

tractor does not move but when the operator presses backwards the tractor moves.  To

provide a little explaination of how the system works the main oil pump is a ball piston

pump with a moveable swash plate that controls the outer ring of the pump.  In neutral the

swash plate is centered and no oil is displaced. When the operator pushes foward the swash

plate moves to one side to pump oil from the resivour to the motors in the axle. There is

no valve to open or close. The farther the operator pushes the pedal the more the swash

plate moves which allows the pistons to pump more oil.  Now to your problem, to keep the

swash plate from dithering there is a dampening piston that pushes on the face of the

swash plate and kind of squeezes it to control small movements.  The piston is pressurized

by the same oil used to move the tractor forward or backward, there are two pistons one

for the forward circut and one for the reverse circuit. In my case the piston had worn

into the surface of the swash plate so far that the o-ring blew that sealed the piston and

all the pressure was lost to the forward direction. The reverse direction still worked

perfectly because that circuit did not have a leak because it feed oil to the opposite

side of the motors to turn the wheels the opposite direction. I was able to get parts

books from Eaton and even though they said parts were not available I called them up and

all of the numbers were good.  I did have one problem new swash plate came in with a

smaller bore for a different pump diameter. I took the plate to a machinest and had him

bore it out to fit the pump ring out of my old swash plate.  Eaton sold the dampening

pistons with the seals installed. Put things togther and it worked great.  

Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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