Review

Make microtrac tracks longer so there is a lower number of them
Close off bed of Truck - needs a gate
Stagger microtrac wheels
Make pivot supported by 4 corners of Frame Module
Modularize cab
Modularize pivot unit - right now it's one with 2 degrees of freedom - make 2 with 1 degree of freedom for modularity.
modularize engine unit in truck

Example:

Tractor Construction Set Critical Modules