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I am looking for parts and information on rebuilding a hydrostatic transmission on a Murray 46-inch lawn mower. Problem is that when the unit warms up, it slows down, and barely goes in reverse. New belt didn't help. I never changed the fluid.

You're going to need some help there, I wouldn't know where to start myself.

2006-05-03 18:16:09 by natureguyusa

this will tell you all you need to know

Basically the hydro has the ability to change directions on a dime without having to stop and manually reverse the tranny. This accounts for better maneuverability and braking power. They provide continual torquing power as well... This excerpt below was taken from hydraulicspneumatics.com and explains the advantages quite well. Here it is......

........The primary function of any hydrostatic transmission (HST) is to accept rotary power from a prime mover (usually an internal combustion engine) having specific operating characteristics and transmit that energy to a load having its own operating characteristics. In the process, the HST generally must regulate speed, torque, power, or, in some cases, direction of rotation. Depending on its configuration, the HST can drive a load from full speed in one direction to full speed in the opposite direction, with infinite variation of speed between the two maximums - all with the prime mover operating at constant speed.

The operating principle of HSTs is simple: a pump, connected to the prime mover, generates flow to drive a hydraulic motor, which is connected to the load. If the displacement of the pump and motor are fixed, the HST simply acts as a gearbox to transmit power from the prime mover to the load. The overwhelming majority of HSTs, however, use a variable-displacement pump, motor, or both - so that speed, torque, or power can be regulated.

HSTs offer many important advantages over other forms of power transmission. Depending on its configuration, an HST:

transmits high power in a compact size
exhibits low inertia
operates efficiently over a wide range of torque-to-speed ratios
maintains controlled speed (even in reverse) regardless of load, within design limits
maintains a preset speed accurately against driving or braking loads
can transmit power from a single prime mover to multiple locations, even if position and orientation of the locations changes
can remain stalled and undamaged under full load at low power loss
does not creep at zero speed
provides faster response than mechanical or electromechanical transmissions of comparable rating, and
can provide dynamic braking.

...$Billy Ray$

2008-01-27 12:26:11 by barry_howard8

Price: $1,999.95 $1,499.95

Powerful riding yard tractor with 20 HP Briggs Stratton engine and 42-inch cutting width
Air induction for improved cutting performance, anti-scalp wheels, deck wash port
Fender-mounted cutting heightadjustment, adjustable seat, and an ergonomic steering wheel

Has anybody else had a problem with the Poulan Riding Lawn Mower with the hydtrostatic (automatic) transmission?

It seems to go out of gear when under a heavy load and then the gears grind (doesn't go back into gear).

You can look at the lawn forums. They have search engines<best to start with and you can also ask:

http://www.lawncafe.com/forumindex.php
http://www.lawnserviceforum.com/

http://www.lawnsite.com/