# What is a hydro rear?



## bobotech (Oct 6, 2006)

I see people mentioning Hydro or hydrostatic rear ends on lawn tractors.

what exactly are they and what is the difference between a hydro and a non-hydro rear end? And what kind of advantages does a hydro rear have over the non-hydro.


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## bugman (Aug 12, 2004)

Better explained by the definition then I could ever explain it.....


Hydrostatic transmission

Hydrostatic transmissions transmit all power with hydraulics; there is no solid coupling of the input and output. One half of the transmission is a variable displacement pump and the other half is a hydraulic motor. A movable swash plate controls the piston stroke to change the pump's displacement.

They are used in the drive train of some types of heavy equipment, diesel multiple unit trains, and applications requiring continuously variable control (such as riding lawnmowers and lawn tractors). Their disadvantages are high cost and sensitivity to contamination.






I have used one before....., its a never ending array of speeds..., slow to fast without clutching.

They are really expensive and require maintenance.... while your regular non hydro (like a transaxle) these days are sealed.... non maintenance.... a transaxle uses gears of different sizes to give you different speeds depending on which gear you select...
Older transaxles were much, much, much more tougher.... and used gear oil that needed to be changed.... 


basically theres no clutching with a hydro.... can pull more, and they say they last longer...
I'd go with a transaxle every time myself though....


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## bobotech (Oct 6, 2006)

Ahhh, I understand. So in a sense, a hydro rear is like a standard car tranny with the fluid torque converter that transfers the engine spinning the outside of the converter to the input shaft on the inside of the converter via an array of vanes. 

And on the other hand, in simplistic terms, a standard rear is just like a manual transmission without the clutch (hence why you have to stop and shift before taking off again).


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## bugman (Aug 12, 2004)

Basically yes.... think of a shift on the go, a manual with no clutching....
A transaxle a manual (but of course have to stop) but the well worn ones you can usually shift em while the mower still rolls.....


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