You can't run the rear seal in the adapter with the NP205 off the back of the NV4500. So remove that seal and everything will slip together fine. There is a double seal on the input shaft on the NP205, so you don't have to worry about cross contamination of fluids. But you should run an extra quart of the Castrol Syntorque fluid in your NV4500 because some will end up inside the adapter.