2005 Dodge Truck Rear transfer case

Quick question if anyone can help out. I have just taken our Dodge Ram truck in for it's 30k service. We are getting ready to tow over 1400 miles and we needed to get it ready for the long haul. Anyhow, when we got to the dodge dealership, they said it was a good idea to get the rear differential serviced as well. We just had it done two years earlier at 15k miles. Well of course, three days later the seal is leaking. So we had to take it back in to get that repaired, for the second time. (It also leaked upon service for 15k). But this time the pumpkin case on the outside looked different. I thought before the case didn't have a visible plug, this case when we looked did have a plug opening on the case outside. Is there possibility they changed the cases on us? We were concerned and thought we would get a second opinion on this issue. Thanks!