863 drive problem

[volleyman]

I just bought a used 863 with no history. 4800 hours. The engine runs fine and the the lift hydraulics react quickly and seems to have good power.
The drive seems very week with no power at idle and a little movement at full throttle. I'm thinking it might be the drive motors, as I understand that the 863 should not roll when not running. This 863 rolled off the roll back when it was delivered. Maybe the seals are bad in the motors? Where would be a good place to start checking? Thanks for any information to get looking in the right direction.

 

[River Fluid Power]

Do you have the serial number? This model has two drive motor options.

 

[volleyman]

514428256

 

[River Fluid Power]

It's a Rexroth.

 

[volleyman]

Are they good , bad, common problems with them?

 

[River Fluid Power]

They are generally good motors. Contamination and hours are what normally get them.

 

[volleyman]

Is it possible that both motors are weak ( seals) because it will roll when not running or is it something before the motors as it seem to affect both. After starting I get a hydraulic alarm on the BOSS system and it shuts down. I filled the h fluid up to the dip stick level.

 

[River Fluid Power]

Do you know if you have servo assisted steering? If you are unsure, you can send photos of the pump.

 

[volleyman]

 

[volleyman]

 

[River Fluid Power]

The first thing I would check is the bypass valve. There are some little hex head plugs sticking out of the side of each side of the housing with threads showing. I think they have a hole through them sideways as well. Make sure they're snug, but not over tight.

 

[volleyman]

Which housing? Drive motor? Pump?

 

[River Fluid Power]

The pump housing. There is one for the left and right drive side of the pump.

 

[volleyman]

Trying to find bypass valve. Would it be on the top, bottom, or side of pump. From the picture of the pump can you tell if it is a M44 or M46 servo assisted or non servo?

 

[River Fluid Power]

It is the M46. Look for red arrows in these photos for bypass location. One on each side. If they are loose, it would allow the motors to free-wheel.

 

[volleyman]

No valve in that position on pump, just smooth casting

 

[River Fluid Power]

It's a rare M46 that doesn't have those. I think you're going to be pulling the motors. You can pull the pressure hoses off of the pump (the ones that go to the motors, marked A, B, C, & D on the casting) and cap the off with steel caps and plugs. Then start the machine and see if the pump will make the engine labor when you move the sticks. If the engine bogs down, then I would pull the motors off. There are relief valves to protect the pump, so you don't have to worry about hurting it.