No Reverse One Side Bobcat 630

[discountufoparts]

So I have this minor gremlin. After my machine warms all the way up 20 - 30 minutes run time. I randomly lose reverse on one side. It will cut back in and out randomly. It may even spin the wheel full power and speed and then completely lose any power and stop spinning and maybe slap back in. I can let it sit for 5 minutes come back and it works fine then it will fail again after 20 or 30 minutes. The amount i use this machine this isn't the biggest issue in the world other than it seems to happen at inoportune moments. Trying to go up a slippery slope or over a small log and then i have to shut it down and wait and fire back up.
This machine has no electrical control sytemss and very simple mechanical and hydraulic systems.

 

[Tazza]

I'm wondering if the issue is a sticky shuttle valve in the drive motor. If it's the style motor i'm thinking of, there is an allen headed plug, the shuttle valve is behind here.

 

[discountufoparts]

I'm wondering if the issue is a sticky shuttle valve in the drive motor. If it's the style motor i'm thinking of, there is an allen headed plug, the shuttle valve is behind here.

I did put a brand new shuttle valve assembly in when I rebuilt the drive motor. I am going to pull that out tomorrow or Friday and see if there is anything in there or a ripped o-ring. I didn't know if maybe the springs inside the motor themselves that hold pressure on the valve plate assembly could be worn out and failing when they heat up.

 

[Tazza]

I did put a brand new shuttle valve assembly in when I rebuilt the drive motor. I am going to pull that out tomorrow or Friday and see if there is anything in there or a ripped o-ring. I didn't know if maybe the springs inside the motor themselves that hold pressure on the valve plate assembly could be worn out and failing when they heat up.

I'd like to think the springs that hold the valve plate in place wouldn't cause this issue. Start with the shuttle valve, hopefully it's somthing simple and easy.

 

[discountufoparts]

I'd like to think the springs that hold the valve plate in place wouldn't cause this issue. Start with the shuttle valve, hopefully it's somthing simple and easy.

Happy 4th!
I did check the shuttle valve yesterday and it seemed to be working fine with either hot or cold hydraulics. I even swapped out half the old assembly from the allen plug side and same thing with both hot and cold hydraulics.
I do remember thinking when I rebuilt it that the pressure plate with the one forward facing seal and one backward facing seals the new seals didn't seem to be quite as strong as the old seals as far as manipulating them by hand to go into the pressure plate.
David

 

[discountufoparts]

Happy 4th!
I did check the shuttle valve yesterday and it seemed to be working fine with either hot or cold hydraulics. I even swapped out half the old assembly from the allen plug side and same thing with both hot and cold hydraulics.
I do remember thinking when I rebuilt it that the pressure plate with the one forward facing seal and one backward facing seals the new seals didn't seem to be quite as strong as the old seals as far as manipulating them by hand to go into the pressure plate.
David

Another thing to add is that the reverse is there for a split second and then there is like a pop and there is nothing in reverse. I might get 1/4 to 1/2 a tire rotation before it blows out. If I reduce engine rpms to about half operating speed the reverse works fine like there is so much pressure its blowing out something in that side in reverse and when I popped the shuttle valve the other day a little bit of air came out as I was loosening the allen plug.

 

[Tazza]

Another thing to add is that the reverse is there for a split second and then there is like a pop and there is nothing in reverse. I might get 1/4 to 1/2 a tire rotation before it blows out. If I reduce engine rpms to about half operating speed the reverse works fine like there is so much pressure its blowing out something in that side in reverse and when I popped the shuttle valve the other day a little bit of air came out as I was loosening the allen plug.

I remember the seals being failry tight on mine, but i think the hydraulic pressure against them makes them seal.
There are relief valves, so the pressure can't get too high.
The air pocket in the shuttle could be because you worked on it not that long ago, it may not have had time to escape.
I'm kind of lost with what else to look for....
The other thing you could do is swap the drive motors over from side to side, see if the issue moves, you then know for sure if it is the pump or motor.