Replacing my waterpump and the new pump didn't come with the drive coupler. And I can't seem to get the old one off. Don't see a retainer ring or anything. New ones are $40. Rather reuse my old one. Any ideas?

 

Try soaking it inside with some penetrant.

 

Oh ok. So sounds like there is no retainer of any kind then. I'll try that. Thanks.

 

No, it just slips on without any retainer. It should be greased when installing and have good o-rings on the splines of both shafts that go in it.