If a hydro fails what part of it fails ???

[eee]

</font><font color="blue" class="small">( <font color="blue"> Same dealer stated that in their experience - both systems are very reliable - but that the 'only units coming in for repair' (albeit infrequently) were the hydros. The gear versions 'disappear out into the customers hands and don't come back' (for repair). </font> )</font>

Also I have seen on this forum that some claim hydro's will not hold up under continous/non stop pulling such as plowing etc. If so what part of the hydro fails? Has anyone ever had a hydro fail ? If so what part of it failed ? What are the early symptons it is going to fail ? I always assumed a hydro could take more abuse than a geared tractor,are my assumptions wrong ?

 

[RickB]

Hydrostatic transmissions fail most often from excessive heat or dirty/ low quality oil. Overloading and poor oil cooler and radiator maintainence cause overheating. Lack of service and poor habits cause dirty oil. False economy results in poor quality oils being used. Plugged filters cause cavitation which ruins the rotating group in the piston pump and/or motor very quickly; a catastrophic failure. Relief valves protect the forward and reverse circuits separately; a tractor thet will move in one direction only probably has failed one or the other. Clutches are the weak link in geardrive units. The dealer that doesn't see any gear units back has a competitor doing clutch repairs he should be getting. We sell dozens of skidloaders, tractors, and commercial mowers with hydrostatic transmissions each year and average less than probably five repairs annually involving the teardown of a hydro unit. Less than one a year involves the replacement of a rotating group or pump/motor unit.

 

[slowrev]

With the electronic controlled hydros, the problem might be in the electronics. More things to go wrong with EHydro than a gear tranny.

Ben

 

[slowrev]

"The dealer that doesn't see any gear units back has a competitor doing clutch repairs he should be getting."

Rick,
That is one of the things I like about gear trannys, Many people can changer their own clutch with no or very few special tools or specialized training.

Ben

 

[eee]

Rick,
Do you see more geared units coming back to the shop or hydro's ?

 

[jinman]

</font><font color="blue" class="small">( With the electronic controlled hydros, the problem might be in the electronics. More things to go wrong with EHydro than a gear tranny.
)</font>

Ben, I think it's also likely that the electronic part that might fail on an E-Hydro would be a component thats on the outside of the transmission and would not require a teardown or splitting of the tractor. I believe most of the variable actuators are integrated into the mechanics of the foot pedal. In the case of the NH Class III TCs, there is a solenoid that physically changes the motor's wobble plate between 9° and 15° to effectively give two gear ranges. I've never heard of that solenoid failing; although, I've heard of the electrical wire coming loose.

 

[slowrev]

Jinman,
True the electronics portion of EHydro trannys are primarially external. But if they break then the transmission is functionally broken too, and must be considered a portion of the transmission if it will not function properly without them.

Ben

 

[johndeere2210]

Our dealership has quite a few of the CUTs out, both gear drive and hydro. Typically a dealership sees only the worst of the worst. We have never replaced a hydro unit but we have replaced several clutches in the gear drive units. The majority of the repairs made on the CUT units are wheel and hub seals on the MFWD. Some of the early 4100 CUTs had problems with the PTO. In tiller applications, the PTO would shear the teeth off the drive gear. Again, I would like to state that for every one of the tractors in for repair, there are 50 that we never see in the shop. All in all, the CUTs are fairly well engineered and built.

 

[gsganzer]

I think that the nature of a hydro, push a peddle forward or back, infinite speed adjustment etc. make people believe it's an amazing complicated gizmo and prone to failure.

The reality is that it's amazingly simple. It's nothing more then a wobble plate pump. The further down you push the forward peddle, the greater the wobble and higher the volume of fluid being pumped. The pump has the typical vulnerabilities of any type of pump. The wrong lubricant, dirty lubricant, debris in the fluid, cavitation or overheating can cause failure. I think a gear transmission on a tractor may be a little more forgiving of poor maintenance, as virtually none of the transmission parts are high rpm's (except for the drive shaft from the engine)

 

[eee]

</font><font color="blue" class="small">( <font color="blue"> True the electronics portion of EHydro trannys are primarially external. But if they break then the transmission is functionally broken too, and must be considered a portion of the transmission if it will not function properly without them. </font> )</font>

Not all of the hydro's have electronics, I am interested in the durability/reliability of the hydro tranny itself. A lot of other things on the tractor will not function because of electronic failure IE: safety switch under the seat.