Long 2460, about 68 model, strong diesel engine ... rear hydraulics will not go up or down, any movement VERY slow and jumpy.. front bucket worked slow, recent Hy. oil and filter change.. found external hydraulic pump, removed and cleaned, put in all new oil again.. front bucket working fine now but no improvement to rear.. Is there a internal pump ?, screen? or ?.. and if so.. location? how to get to it replace or clean it too ?.. have old owners manual but nothing saying where another hydraulic pump or filter might be located.. Appreciate any help.. Thanks