Drive/Transaxle Leak at Pressure Relief Valve

[melgibson]

I'm just writing to see if anyone else has had this problem and has found a solution.

Attached is a picture of the pressure release valve from the rear drive/transaxle unit of a D series, so you can see what the part looks like. I get a significant amount of hydraulic fluid leaking through this valve (more when we're pushing the machine, less when we're just 'tooling' around).

Since the transaxle is filled with gear oil and the attached drive motor is powered by hydraulic fluid, you'd think it is a drive motor seal issue (although I still can't figure out why there is not hydraulic fluid in the gear/transaxle oil - looking at the parts diagrams it seems like there should).

I've had two other forum members contact me with a similar problem. Like my own experience, Bobcat and the local dealers don't have any idea what is causing this and they want to charge a significant amount of money to 'learn on the job.' One of the other owners was going to have Bobcat do it, but he changed his mind and pulled the drive motor and replaced the seal himself- but it didn't work. Unforntuately, these drive motors, and the pressure release valves, are made by an outfit in Italy and I haven't been able to get any help from them either.

Meanwhile, I continue to buy replacement hydraulic fluid, and my beautiful machine always looks like a mess.

So, has anyone else had this problem, and has anyone found a fix?

 

[SSdoxie]

The transaxle is limited slip so uses transmission.differential fluid compatible for limited slip differential. The axle also has wet disc brakes, the anti-wear additives in the hydraulic/hydrostatic fluid will soften the disc brake and allow more slippage thus leading to pre-mature brake failure. The leak in the drive motor seal is a symptom of the real failure, not failure itself. Seal could simply fail and replacing it repair the problem but if seal was replaced and problem is still there then other causes need to be inspected. Either motor has excessive wear/by-pass, or the case drain circuit is restricted casing high back-pressure forcing oil past the seal. Change the case drain filter and inspect the drain hose from motor to filter to tank making sure there is no kinked, pinched, or collapsed line.
Once that is done, replace the seal then tee in a guage at the motor case drain fitting and check the pressure with motor spinning at full speed and under power if possible. I would not expect to see any more than 15 psi on a good circuit.

 

[melgibson]

Dennis, thank you very much for your reply; I can't tell how refreshing it is to find someone who knows their stuff.