A new Genuine Meyer 15606 Crossover Relief Valve. If you don't want this style, we also sell the new one piece. This was used on many of the Meyer plow pumps including E-45, E-47, E-48, E-57 and E-60. This comes with all the parts and the seals. This valve is designed to let fluid bypass if you hit something. When they go bad, the plow will often drift without much weight against it. They can be tricky to install, but if you take the old one out one piece at a time, you should be alright. The spring is known for deteriorating. If that is all you need, we sell them separately too.
Below are some rebuild manuals to show you how to install: