[theduke]

You cleaned the screen for hydraulics?

Possible the seals in steering cyl are leaking internally.

Do you have a copy of repair manual??..if not I can post a link here in a bit

 

[theduke]

I think its an 855 He's got.
They don't have that part you showed as/drag link.
There is no steering box . Its all lines on a 955 which is what His late model 855 is based off .
Just a wheel to wheel tie rod and a hydro cyl mounted to front axle.

 

[theduke]

IIRC
The 850 1050 and probly several others of the "gear" drive were the Yanmar built...jd badged.
They do have a steering box and some had/have gealer added PS like what you show in place of drag link
Neighbors 1050 is built that way...why it has PS and No loader we can't figure out.