Keep blowing final drive seals. The last on cracked the case cover. Hydraulic oil in the gear box. I was told by the final drive repair man that 331 and 334 has this issue. Apparently a valve malfunction causes pressure to go through the return lie to the final drive blowing the seal. He said if I run the machine there would be pressure in the return line. Anybody know which valve? Is this possible? I have run the machine with the covers off and get no pressure on the return lines. I have run all the operations and still no pressure.... This is the third seal in 8 months. This time the controls got stiff and Bang. There goes the cover plate and here we go again. Thank you for any advise.
We have a final drive troubleshooting section on our FDC website, see my sig below. Are you blowing off the outer cover? I sell over 100 Bobcat 331 drives a year and most of the failures are due to lack of maintenance. (not changing gear oil) I've never heard of a valve problem causing this. I'm not sure what repair man you are referring to, but I think what they are describing to you is improper hose installation. This IS a common problem when replacing a travel motor. People often get the hoses mixed up when reinstalling. Usually it's two scenarios: 1) Forward / Reverse line inadvertently hooked up to case drain port. The unit would operate fine in one direction, but when you tried to go the other direction the machine would slow down, come to a stop and then POP!! There goes your outer cover. High pressure oil gets sent down into the return port, it has nowhere to go. It fills the motor with hydraulic oil then has to go somewhere. So it blows the motor shaft seal, fills up the gearbox with hydraulic oil and then finally builds enough pressure to blow off the outer cover. This would happen in a matter of seconds. 2) Case drain and 2 speed line inadvertantly switched. The unit would operate almost 100% normal in low speed. However, once shifted into high speed it would do the same as described above. Although it usually does not happen in seconds. We have heard of everything from instantaneous POP, to running hunderds of hours before catastrophic failure. Your forward and reverse lines are the largest two lines, on your travel motor they will bet the two 3/4" UNF ports in the middle. Your case drain line on your unit will be on the outside on each side of the forward and reverse lines. It is a 9/16" UNF port. When installed on the machine, you will use the top most port. Your two speed line will be the only port not in line with the others. Here is the frustrating part...it is the same 9/16" UNF port as the case drain. You can see now how it is easy to mistakenly hook up. An easy way to determine which hose is your case drain line is to blow air up it. Whichever lines bubbles in the tank is your return line. I would start here with making sure your lines are correctly installed. Hopefully you tagged them and can go to machine and determine whether it was connected properly. If it was, then we can start troubleshooting other parts of the machine. Although I think it is unlikely that it is something else. Check our FDC site, we have a "Motor Connection" page that should help you if what I typed is not clear.