The info should be in the HLR (Hi-LO-Reverse) transmission section of your manual, but they don't spell out there is a seal here , here, and here, as line items. You need to read the repair procedures and see where they say to replace a seal , O-ring, or gasket as part of a component overhaul, like the clutch pump. I expect you are looking at a John Deere technical manual for a 450. I don't have one so can't tell you the pages in your manual, but from the manual I do have information is in the HLR section. You will be looking at seals, O-rings and gaskets in the transmission front cover area and the Clutch (or HLR) pump which is around the input shaft. You will need to study the parts book as well to find the parts you need.
Here is a link to the transmission area of your crawler. There are two transmissions here so be sure you look at pages for the HLR transmission.