I have a 2007 d6n that the steering has gradually gotten worse on. If it's not under full power it wont turn in any direction. It's not making any odd noises from the hydraulics. Not really sure where to start. Are There any solenoids or actuators that can be changed or tested first? I dont have the setup to test the hydraulic pressure either.
I think you'll end up having to check pressures. From what I remember those dozers have a steering motor. Guess its possible that the motor could be starting to leak internally.
You need to check pressures it has differential steering
Isn't differential steering an option? A serial number would probably help.
The way he explained it it sounded like it has it
D6N was available in both Steering clutch/brake & differential steering versions. Although it does sound like the OP has a diff steer machine it would be nice to have a Serial Number. It makes looking up information far easier.