First of all lets start with the CAT trucks, ALL OF THEM has the same problem.
Rear suspension is completely stiff. That is why I will not even use them.
GMC Brigadier 8000.
There is a collision when sparewheel is installed. Its too far to the front. It hits the transferbox and if crane is installed it hits the support leg too. You can find the same problem in GMC MH9500 but there its less of a problem as the spare is further to back already. Simple to fix by moving the sparewheel more to the back on both of these trucks as there is room for that.
GMC trucks spare wheel hits small crane and transferbox, all cat trucks rear suspension