Exactly what happens if you tow a hydro mower without releasing the hydros?

I know to release the hydros before towing a mower, but a friend of mine didn't. His mower died on his lawn and he couldn't get it running again so he towed it to his garage with his truck without releasing the hydros. He said it pulled fine without skidding. It's a pretty big yard so it could have been for 100s of feet. He has a Bob-Cat Predator Pro with the Hydro-Gear pump and Parker wheel motor combo. I showed him where the releases are and told him not to do that again and that he could damage the transmission. He wants to know what damage he may have done. He got it running and he says it seems fine. Should he change the fluid and filter after having towed it or anything? Just how bad is it for the this style transmission?

Darryl,

I have been thinking about your question and I do not know what damage it will cause, but I suspect that it may be fine. I do know that my Exmark has a hydraulic system with separate pumps and motors and I cannot move it/push it at all without engaging the bypass. With that being said, it may be possible to tow it with a heavier, more powerful piece of equipment or a vehicle. The hydraulic systems are somewhat sealed to the extent that air shouldn't have made its way down into the pumps and any internal, moving parts on the motors and pumps likely didn't take any damage from a tow, especially if done carefully and slowly. Knowing that the mower is driving just fine after this, would lead me to believe that no harm was done. If no leaks, no pull to one side, or no loss of power, than it's likely to be okay. But, if something does go wrong anytime in the near future, of course your friend will certainly attribute the failure to that one time it had to be towed without the hydraulics being released.... Hopefully all is well!!!

Thanks for the reply. I'll be visiting the Bob-Cat dealer where we both bought our machines within the next week or two and I'll see what they say and report back here as a follow-up.

Im not an expert but in my opinion the only important thing it effects (depending on model) is the warrenty. If he has a warrenty and he admits he did that it will void any drive train or hydrolic warrenty he had. Having said that its still a bad idea to do it as a practice because the trans will get 0 cooling while you tow or push it. If you tow it like that it wont take very long to cook a transmission and even if it doesnt cook it gets hotter than normal which gives it excessive wear and tear. This translates to failure sooner or increases the chance of cooking it the next time it happens. Thats the short answer and what really matters. Post what the expert says and let me know how good or bad of a answer i gave. The only think i hate more than being wrong is being wrong and not knowing it but everyone else does. lol

The trouble with towing is you are working the system backwards.
This in itself is not all that big a problem as the pump & wheel motors are basically the same units although the oil ways will be out of time.
The problem is to go backwards the input pulley needs to be able to move freely, which it can't because it can not turn over the engine backwards.
This causes very high oil pressures which will get relieved by leakage between the valve chest & the valve plate.
There is no seal there so oil being forced between the two faces will damage the faces and then when trying to operate as normal, you will get excessive leakage .
The result of that is the "Hydro Howl" followed by the owners howl when they get the repair bill.

So if you have to tow the unit, remove the drive belt.
It won't stop any damage but it will limit the damage done.

bertsmobile1 said:

The trouble with towing is you are working the system backwards.
This in itself is not all that big a problem as the pump & wheel motors are basically the same units although the oil ways will be out of time.
The problem is to go backwards the input pulley needs to be able to move freely, which it can't because it can not turn over the engine backwards.
This causes very high oil pressures which will get relieved by leakage between the valve chest & the valve plate.
There is no seal there so oil being forced between the two faces will damage the faces and then when trying to operate as normal, you will get excessive leakage .
The result of that is the "Hydro Howl" followed by the owners howl when they get the repair bill.

So if you have to tow the unit, remove the drive belt.
It won't stop any damage but it will limit the damage done.

Click to expand...

Thanks.

The force of the fluid could blow the seals out around the axle seals which will cause leaks and then failure from fluid loss and then from dirt getting into the seals and into the gears. Pilot shaft where wheel bolts to the wheel motor or transaxle is the weakest point and leaks there most of the time when they fail.