Yes, that's normal. I was going to mention it earlier but I didn't. IRL you can't have a rear axle without the diff housing... it's what connects the axle tubes. The only way to build a trailer out of a pickup truck and not have a diff housing under there would be if you transplanted a beam axle from the front to the back... which would be a ton of work for almost not benefit. For reference, see this picture from fourwheeler magazine - http://www.fourwheeler.com/how-to/t...raightening-a-bent-dana-44-axle/photo-11.html
I've never seen a long bed made into a trailer IRL. I assume that the resale value of the long bed and other related parts precludes turning it into a trailer. As @Peterbilt said, these don't exactly make great trailers when they're done.
I haven't expected that those trailers exist irl so I made it like something that's made like this from factory. Anyways, I'd also be possible that someone was bored, removed the diffhousing and welded a segment of another axle tube inbetween, or took a fresh pipe as the axle and added the nessary suspension mountings.
With my Buddy's old Ford truck trailers, two of them are half ton, the other two are 3/4 ton, all long bed, all with just the pinion and ring gear removed from the axles. They are a pretty common sight, usually what happens is someone will wreck an old truck that isn't worth saving, so they cut the frame off right behind the front axle and fold the frame rails together into the tongue, stick a hitch on the end, and viola! You have a trailer.
Interesting. Around here truck trailers are becoming much less common in general. Long beds have never been common here, I guess it's different where you are?
Exactly what I did - in blender, hehe That music though...yep, like the ideas, especially the spare-tire one.