753 bobcat drive line

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ScottMc

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Oct 17, 2017
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4
Hi all, I'm a new member and new to skidsteers. I bought an old 753 with a genuine 1600hrs on the original engine pumps etc. I'm sure that there has been similar posts previously but I am having trouble searching them out. I have good drive strength (spinning wheels when against an immovable object) but I find that when I pull the sticks to the rear that the left side seems to not drive until I reach near the end point of the stick travel or I push forward on the left and then quickly to the rear. I assume that it is perhaps some kind of sticking valve?? Could someone please point me to previous posts or point me in the direction of possible causes that I can investigate. Thanks in advance
 

farmshop

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Mar 27, 2014
Messages
698
Does it drive straight going forward and reverse? Does it push against the park break or creep when not locked? It could be a linkage adjustment. There are bushings in the links that could be wore also
 
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ScottMc

New member
Joined
Oct 17, 2017
Messages
4
Does it drive straight going forward and reverse? Does it push against the park break or creep when not locked? It could be a linkage adjustment. There are bushings in the links that could be wore also
Thanks for your input farmshop, I spent a fair amount of time under the cab adjusting the park brake yesterday. I had a look at the main linkages at the same time. There did not seem to be any significant wear or slop in the linkage or levers. The machine drives almost perfectly straight with an ever so slight tendency to veer left. There is no creep when stationary and I have not noticed it veering to either side when reversing. It seems to be a very sudden change when it happens.......like a valve has gone from closed to full open.
 

farmshop

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Joined
Mar 27, 2014
Messages
698
Thanks for your input farmshop, I spent a fair amount of time under the cab adjusting the park brake yesterday. I had a look at the main linkages at the same time. There did not seem to be any significant wear or slop in the linkage or levers. The machine drives almost perfectly straight with an ever so slight tendency to veer left. There is no creep when stationary and I have not noticed it veering to either side when reversing. It seems to be a very sudden change when it happens.......like a valve has gone from closed to full open.
I believe there are springs on the pump linkages could one of them be goofy
 
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ScottMc

New member
Joined
Oct 17, 2017
Messages
4
I believe there are springs on the pump linkages could one of them be goofy
I've looked pretty well at the service manual and the machine and it would appear that there are no springs on any linkages. The pintail arms are connected via a pivot bush to the levers. The centering plate that covers the pineal levers has a cantering spring located at each side but I would think that if it were getting stuck that the levers would not be returning to their neutral positions. The workshop manual suggests that the cause could be a sticking hydrostatic pump replenishing valve but I can see no reference to where this valve is located or how I would service it/clean it. I assume that is is probably behind a whelch plug somewhere but I am not sure where to start. I'm fairly mechanically minded but not so familiar with hydraulic systems. I appreciate the suggestions you have given me so far. Do you think I have posted in the correct forum or should I try another area? Thank for your time so far
 

farmshop

Well-known member
Joined
Mar 27, 2014
Messages
698
I've looked pretty well at the service manual and the machine and it would appear that there are no springs on any linkages. The pintail arms are connected via a pivot bush to the levers. The centering plate that covers the pineal levers has a cantering spring located at each side but I would think that if it were getting stuck that the levers would not be returning to their neutral positions. The workshop manual suggests that the cause could be a sticking hydrostatic pump replenishing valve but I can see no reference to where this valve is located or how I would service it/clean it. I assume that is is probably behind a whelch plug somewhere but I am not sure where to start. I'm fairly mechanically minded but not so familiar with hydraulic systems. I appreciate the suggestions you have given me so far. Do you think I have posted in the correct forum or should I try another area? Thank for your time so far
I think you have posted in the right spot. You are probably approaching an area of service many on here wouldn't try to tackle. You have ruled out the simple things. As long as your control linkage moves the valve during the whole range of motion of the lever you are probably correct in thinking it's a valve
 
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