Read the README in the file.
One of the biggest issues I've seen and been talked to about is the truck getting stuck quite frequently on unlevel surfaces but I've fixed that issue and you shouldn't have anymore issues.
* Realistiic Sounds (best that's available) XML to change sounds is included in download.
* Fixed back axles (no more getting stuck)
* Leveled the peterbilt (front was slanted down, back was slanted up)
* Fixed some appearence issues (decals, lights)
* Fixed exit point (no longer exit in sleeper)
* Added chassis cover (thanks to Aaronamy)
I still have a few parts that aren't aligned properly so there will be a fix to those in the next couple days. If you don't know what parts i'm talking about then good, you don't notice.