This is based on my 3-axled lorry with pendular suspension, in that the rear three quarters of the chassis, 2nd, 3rd and 4th axles, 6 cylinder in-line engine and drive train are essentially unaltered.
However it has an additional steering first axle, and a mechanically-raised tipping body. All four axles have pendular suspension.
About this creation
Before raising the tipping body, the operative releases the tailgate catches and places the supporting struts in position on the tailgate.
View of the mechanism for lifting the tipping body. A worm screw acts to turn pinions which move a pair of racks back and forth, which in turn push a set of rods which lift the tipper. The mechanism can be operated via a wheel on either side of the lorry, behind the engine.
The gears between the two rear axles' differential gears and the propellor shaft can be seen beneath the lift mechanism.
The differential steering rate for the two steering axles is achieved by using longer steering arms on the 2nd axle, with both steering axles controlled by identically sized pinions on a single shared spindle, avoiding the need for a complicated gearing system. The advantage of this is that all steering wheels are in perfect alignment when the steering is in the straight-ahead position. I don't know how realistic the differential steering rate actually is though, but it seems to work fine.
The following sequence of pictures show various axles' pendular suspension coping with a lego plate beneath the tyres.