I always wondered about that little green plug was all about. I thought maybe it was to identify what gear was in the rear end like 345, 410.456 via a quick look for that color. Problem is I have never come across another Dana with a different color on it. Last week I did some research for a friend that has an ex Pro Stock Cuda that has un uncut Dana B Body length rear in it and the rear end has the green plug. Any one else has an idea of why there is a green plug and if there were any other colors. I will see what gear came in this rear end and maybe if we can amass enough information some answer can come from every ones information. I know none of the Dana Rear ends have this plug I own. Two of them are 410s, one a 456 and the other 354 now 538.