450 (straight)crawler/dozer hydraulic filter change

[2378]

Hello My hyraulics quit working , almost suddenly although they were never fast, the left and right angle still move but extremely slow no up, no or L & R tilt . I recently had the entire blade off so all the hoses were undone .Thinking i may have got some dirt.When i removed fill cap i still pressure, i am pretty sure the pump is still working.
So i looked into things and found out about the 2 filters in the hyd tank . Thought i would start with the easiest things first or so i thought.
Removed all the bolts in the plate/access on top of the tank but when i went to lift out the filter the whole thing will only come up maybe 3/4" and something is hitting . I have never cleaned/ changed these filter and would be very surprised if the previous owner ever did.
Any ideas as to what this could be holding it from coming out? Has anyone ever had a similar problem ?
Any and all suggestions would be appreciated.

Thank You
Mike