Tractor severe understeer

[Keycare]

I have a 1984 MF250 with Hydraulic assisted steering. I have managed to get the hydraulic steering working again, however, the tractor seems to want to keep going straight on when I turn the wheels beyond the 5 past/5 to the hour mark (12 o'clock being straight ahead). Very severe understeer. My friend has a MF135 without power steering and it turns far tighter and doesn't seem to suffer from this so I am sure it is not right.

I thought it might be the diff-lock sticking but the plunger seems to move freely. Are there any tests I can perform? Or do you have any other ideas why this might be happening.?

Thanks.
Richard.

 

[mjw357]

does it have left/right brake pedals? if you brake hard with one pedal, does the tractor turn that way or does it want to stall?

 

[davesl708]

It sounds like the steering hyd. cylinder is allowing fluid to bypass the piston inside the cylinder. The o rings maybe worn or damaged. Did you rebuild the cylinder to get it working?

 

[Keycare]

Thanks all.
I tried the breaking suggestion and found that the diff lock was sticking on, hence fighting with understeer. So I worked the footswitch with some lube and the plunger with a pry-bar and managed to free it up. The tractor now turns properly. I just hope I haven't damaged the diff.

Cheers,
Rich.