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Repair information and troubleshooting for Craftsman-brand riding lawnmowers.

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Why does hydrostatic transmission whine when brake is released

Tractor transmission does not whine when brake is engaged, but when brake is released and tractor moves forward the transmission whines.

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Great detailed answer. Thank you.

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I have a PRO Z Force 100 60 in Cub Cadet. It's 3 years old and I keep it served regularly from the dealer that I bought it from. I recently brought it home and after about the second or third use, all of the sudden it's making a whine noise just as soon as I dis-engage the brake for it to go in gear. The moment I lock in the brake pedal, it goes away.

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The brake stops the tractor from moving, so the hydro-static drive isn’t spinning; which is why it’s silent.

You didn’t list a model, so I can’t look up the owner/maintenance manual for it.

I’ve had and seen many drives of this type make noise, and depending on the age and use, it’s probably from normal wear and tear on a well used piece of equipment. I have seen a couple Husqvarna models make this noise from the factory, my dad’s did, and he used it for almost ten years every day.

Some noise is normal; your engine is basically driving a hydraulic pump, from a belt which goes from it’s crankshaft pulley, which in turn, drives the hydro-static drive axle. Don’t confuse this with the actual PTO that drives your mower deck blades which is either electronic or manual. That pump is moving fluid to cause the mower to move forward at multiple speeds, or reverse. Older mowers used an expanding v-pulley to change the forward speed ratio. The hydro-static drives vary the amount of fluid being pumped to achieve the same goal.

One of the things to check, and the method varies on some makes, is to purge any air that might be inside the drive axle; and or change the drive fluid. With air in the drive, it can be more noisy than it should, older fluid can be a cause also.

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just changed the hydro fluid on my JD LA 140 with the recommended viscosity and now it whines and looses forward drive... any suggestions on how to purge the system ??? please

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make sure fluid level is full. Sometimes when you change oil and put new oil in they get air in it. so run it. then check and fill to its proper level.

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