Try one thing before you blame the wrong parts. Raise the loader and listen with a stethoscope or even a piece of pipe against the bucket cylinders. You will hear a hissing/whooshing sound it the cylinder packing is leaking. This is oil bypassing the O rings on the piston, when the oil transfers from one end of the cylinder to the other of course the bucket tilts.
As pogobill has given you the website for agco manuals, you can purchase operator, parts, service manuals for the tractor and loader. Beware of one thing though for the service manual the "packet" contains the same information as the "assembly" the only difference is the assembly comes with an (expensive) binder. You can also go at
www.agcopartsbooks.com and find the parts for the tractor and loader. You can even print pages or if you are so inclined and have patients you can print the parts page by page.
If it works here are links to the pubs
according to the parts book
71511608
SEAL KIT
Should be the seal kit for the bucket cylinder.