1995 Bobcat 753 drive issue

[drmstk]

I just bought a Bobcat 753 a week ago. I didn't pay much for it because of the right drive motor issue. I bought the o-ring kit from Loader parts source and everything went well. Right drive motor works now. My issue is when I push the right stick forward, it activates both drive motors evenly and goes straight. I just use the left stick to steer either way. Reverse acts the same. If I push only the left stick forward it goes straight forward as well and use the right stick to steer. Reverse works the same. If I push both sticks forward it goes straight but seems to fight me getting there. Shouldn't each drive motor be separate from each other like my zero turn? Is there maybe a bypass that is activating?
A little history. It has over 6000 hours. Hydraulic fluid had water and was white. I drained all I could when changing drive motor seals. Bought extra hydraulic fluid to flush out again very soon. I did not change case filters or the main hydraulic filter yet but have them in today. Could one of the case filters be plugged up from the o-rings from the right drive motor? The o-rings were almost gone so I know they are in a filter somewhere. Maybe the one under the tank. Thanks in advance for any ideas on what is going on.

 

[KyMadMan]

It could be a clogged filter, but I would check the adjustments on the controls. Someone might have adjusted them to compensate for the weak right drive motor. Make sure nothing is binding and check the movement of the controls without the motor running. You are correnct, each side should work independent of the other.

 

[drmstk]

I bet you are right. I did see white marks on the flat bar marking the current adjustment. I will check it all when I get a chance and reply back. Thank you!!

 

[drmstk]

Just finished up my house build where I did most of the inside finish work. Sorry for the delay in follow up.
I am now trying to break the hard packed rock with the 753 so I can use my subcompact to level the yard. I checked steering and it looks like all of the pintal arms and bushings were replaced on both steering arms and everything is lined up perfectly. Someone tried to get the right side working as there are new hoses and everything is clean. I just don't have much time to tear it all apart until the Fall, plus it is hot/humid as can be here.

After a couple of hours on it this week, it does not go forward on the right side until the steering arm is all the way forward then it jerks like crazy like there is air in the line or I can push both arms and it seems to go forward but pulls towards the right then jerks to straighten it out. Reverse works perfect on both arms and it acts pretty much normal. It is kind of dangerous around the new home. The right drive motor still feels strong as can be when any of that happens so I think something is plugging up in the pump, like a relief valve, or a plugged filter as you said before. I was thinking about switching things around to see if it follows. Like the reverse and forward hoses or even the drive motors but sure hate wasting all of the hydraulic fluid at $50 per 5 gal.

I will let you know what I figure out soon and please let me know if you have any ideas on things to try.

Thanks!!

 

[Old_853]

New filters, fresh fluid, then chase the what if's. It will likely work fine. These machines aren't cheap, and contaminated fluid will ruin your day every time. Buy 20 gallons of fluid and another set of filters, so you can change it again after a few hours of runtime. Don't destroy the machine over $100 in fluid. Fix it up and sell it for more than you paid for it when you're done with it.

 

[drmstk]

I will take your advice on the fluids and filters as well. Thank you!!

 

[drmstk]

Is there a certain spot to drain all of the hydraulic fluid? I picked it up on my lift and saw a plug down in the back middle but wasn't able to budge it. Is it possible to drain all of it through the aux port with a short hose? Or will that make a mess? Last time I changed the right drive motor, it came out of a few spots under the belly pan. Would love to completely drain it and start fresh with all new filters. Thanks in advance!!

 

[Old_853]

The case drain (little hose) on the motor will get most of it. Some people just hook up the aux ports and let it idle until you hear the pump whine. The two plugs in the recessed port in the back are for fuel and to drain the chaincase. The side ports just drain what you spill from the drive motors. I try to keep both clean when pressure washing, they get gunked up pretty bad over time.

 

[drmstk]

The case drain (little hose) on the motor will get most of it. Some people just hook up the aux ports and let it idle until you hear the pump whine. The two plugs in the recessed port in the back are for fuel and to drain the chaincase. The side ports just drain what you spill from the drive motors. I try to keep both clean when pressure washing, they get gunked up pretty bad over time.

Good info! Thank you!!

 

[drmstk]

The last couple of nights, I took y'all advice and drained the hydraulic fluid and swapped both drive motors. Installed fresh hydraulic fluid, 2 new case filters, and a new hydraulic filter. It now works great going forward on both sides. The crazy jerking is now on the left hand side but only in reverse. The jerking seems to be way easier to handle in reverse than forward. It was 10 Pm last night so I only ran it for 5-10 mins. I will do more testing when I get more time. Looks like I need to go back into the drive motor I rebuilt in March. Either I did something wrong, blew another o-ring, or something is really worn out in it. Guessing I missed something. I have an extra o-ring kit so more to follow soon. Thanks for all of the tips and advice!!

 

[drmstk]

I spent a few hours on the 753 today and it is much easier to drive with the jerking issue on the left reverse. I do find it doing well in forward now but it is jumpy. Really hard to smoothly pick up a load out of the pile or just drive forward. It will sling you all over if you let it. I tried different rpms and grabbing the handles on top and down load bracing on the bar thinking it would help.

Could it be the hydraulic pressure needs adjusting? Only mentioning that because the tilt cylinder was rebuilt just before I bought it and just wondering if too high, it might have also blown out an oring in the drive motor I had already rebuilt.

All in all, I was able to spread a whole load of sandy loam until the tilt cylinder started leaking. After a while it was bad enough to start streaming out. I shut it down and it now needs another night of maintenance. Parts on the way.

 

[Old_853]

I just blew one of the tilt hoses on mine, the ones in the back where the lift arm flexes. The only reason I noticed is because it started getting jerky. Air gets in the system and ends up in the drive motors, pump, etc. I don't have one, but if you had a gauge to install on the quick disconnect aux circuit you could test pressure pretty easy. The other thing it could be is mechanical. Your drive motors attach to a gear reduction. When the bearings let go in that the shaft wobbles binding the gears and chewing them up. Try putting it on jack stands and running it forward and backward. If you feel popping like gear teeth binding, that's probably it. You should find a manual for your model, and read up on it. It's hard to diagnose problems over the interweb.

 

[drmstk]

I spent a few hours on the 753 today and it is much easier to drive with the jerking issue on the left reverse. I do find it doing well in forward now but it is jumpy. Really hard to smoothly pick up a load out of the pile or just drive forward. It will sling you all over if you let it. I tried different rpms and grabbing the handles on top and down load bracing on the bar thinking it would help.

Could it be the hydraulic pressure needs adjusting? Only mentioning that because the tilt cylinder was rebuilt just before I bought it and just wondering if too high, it might have also blown out an oring in the drive motor I had already rebuilt.

All in all, I was able to spread a whole load of sandy loam until the tilt cylinder started leaking. After a while it was bad enough to start streaming out. I shut it down and it now needs another night of maintenance. Parts on the way.

Follow up on the replacement of the tilt cylinder seal kit.

I was able to change out the seals and everything went well. It is a very messy job even with trays and pans around. I found my seal kit locally too. I'd say the tip on Lucas assembly lube was the ticket. It is some slick stuff and everything was super easy to put back together. Figured I would share the part number info for my 1995 753 seal kits.

lift seal kit 7137769 $108

tilt seal kit 7135551 $123

 

[Jim A]

Check charge pressure while operating.

 

[drmstk]

Thank you!! I will read up on how to test charge pressure.