I have an 04 Envoy SLT 4 by 4. I have to replace the axle bearing and seal because of a leak. My fill plug on the axle is froze. So I need to replace my differential cover. With one that has a fill plug. But I don't know what kind of axle I have. Therefore I cannot find a cover that fits with a fill hole. Does anyone know? Of one out there that will fit. That has a fill hole.?