Re: whats the gCwr of your bus? (combo weight/w-trailer)
I've seen a few school busses in the past year, but I've not seen a single GCVWR for a single one of them.
This is an option for the manufacturer, and really depends on a lot of factors. A major factor is the actual hitch installed, and most school busses don't come from the factory with a hitch.
There's a recent thread where the total weight limits for the AT545 and MT643 transmissions are referenced.
In my opinion, the smart way to do this is to take the max weight the transmission can handle and treat that as the GCVWR, pre-supposing you have a hitch installed properly and rated for the weight required to meet that GCVWR.
I'll be really surprised if anyone does have a GCVWR from the manufacturer. On the other hand, I'd love to be wrong about that. In my opinion, chassis manufacturers should include that figure just like GVWR.
Unfortunately, I suspect that the GCVWR being missing puts you in a grey area of the law, where things aren't clearly defined.