Cat 268B drive/steer problem

I'm working on a 2009 cat 268b with poor drive and steer function. When the machine is started it pulls in reverse against the parking brake. When the brake is released it want to roll all over the place like the joystick is not in neutral. The machine rolls and steers but has a huge delay and no power/speed no matter the rpms. The left joystick pilot valve was replaced due to excessive wear and leaks. Lift and tilt work perfectly. The engine and pumps were replaced by cat. I'm not sure if I'm looking at a relief problem or electrical issue.

Hi, serial prefix LBA?
What do you mean, rolls all over the place when you release the park brake?
When it" rolls" is it always in the same direction?
Did you have this problem before the joystick was replaced or just leaks ?
Was the complete joystick replaced or different sections?
Have you had the joystick apart especially the lower resolver section?
Why were the engine and pumps replaced ?was this before or after the problem started?
Mark

Mark250 said:

Hi, serial prefix LBA?
What do you mean, rolls all over the place when you release the park brake?
When it" rolls" is it always in the same direction?
Did you have this problem before the joystick was replaced or just leaks ?
Was the complete joystick replaced or different sections?
Have you had the joystick apart especially the lower resolver section?
Why were the engine and pumps replaced ?was this before or after the problem started?
Mark

Click to expand...

As soon as the engine starts you can feel the machine pulling in reverse against the park brake. when the brake is released it wants to roll backward like the joystick is not finding neutral. had the problem before the joystick was replaced. the complete lower joystick control valve was replaced with a cat part. I don't know why the engine or pumps were replaced, a friend of mine just bought it and dropped off for me to look at. i'm presuming that the problem started after the engine and pumps were replaced. the serial number is CAT0268BELBA00492

In Mark's absence see if the attached is of any use to you.
You'll need to get the machine securely up on blocks so that the wheels can turn freely.

Nige said:

In Mark's absence see if the attached is of any use to you.
You'll need to get the machine securely up on blocks so that the wheels can turn freely.

Click to expand...

thanks so much for the info that is very helpful

Make sure to supply feedback of what the outcome was once you get the problem sorted.

Nige said:

Make sure to supply feedback of what the outcome was once you get the problem sorted.

Click to expand...

after some delay i was able to get back this project and a found a few things. First, as soon as a start the machine the tires are trying to roll forward against/through the park brake. The park brake holds the machine in place. Once I release the brake both left and right side drive tires roll forward at the same time pulling the machine straight.

I have the machine on four blocks with all tires off the ground and have it setup so I can run the machine with the cab up. In the file you sent me there is a Neutral position test/adjustment. In the document the test states that is is only used if tires on one side are spinning faster than the others. If this is the case, is there another procedure to get the machine not to roll with the joystick in the neutral position? i didn't want to start moving the adjusting screws and make it worse.

Based on the point that all tires are moving in the same direction at the same time is it safe to presume that the pump is synchronized? Also, what is the procedure to test the pump to ensure its not junk. I apologize for the ignorance, I deal primarily with Bobcats.

No apologies necessary. TBH you really need someone like Mark to advise you on where to go from here. But FWIW I think the pump neutral position test is still the one that applies because part of the text of it is as follows - "If the pump is not synchronized, ...... the machine could move with the pilot operated hydraulic control ( hydrostatic) in the NEUTRAL position." This is what is happening to your machine.

Even though the procedure states that if the wheels start to turn at the same time it is not necessary to carry out the procedure, the statement above seems to indicate that it is.....