Had a great first time session on the DangerDogz server yesterday with a couple of my squad mates working on the tanks, both modern and WWII.
All three of us had no engine sounds in all of the tanks we tried, Abrahams, T-80, Sherman's, Panzers.
Gun sounds were fine, just no tank engines. A couple of the trucks we also tried (can not remember which ones) were ok.
Server is running the open beta version.
There were mods installed on the server and obviously our machines, which I know you don't like for bug reports but all we had on the server is the A4-E, the Bronco and the T-45, nothing else. These are all long established mods which I feel sure would not be a cause.