4908 aluminum diff cup

I ordered the FLM13010 for my 4908 diffs not thinking about them not being sealed, as soon as i got them I realized they wouldn't work. I am hoping FLM51000 for the new 3905 will work for the 4908 since the both use the Revo diffs. The only thing I don't know is if the insides are the same even though the 3905 use the I-bar. It also says the 3905 diff cup will work with the Revo and since the Revo is almost exact to the 4908 I think it would work, has anyone ever tried?