The 4WD was partly involved when fire crews from Roxburgh and Millers Flat arrived at the scene just after noon.
Traffic management was in place as both lanes on the Fruitlands-Roxburgh Rd, near Shingle Creek, became congested.
A Fire and Emergency NZ (Fenz) spokesman said the vehicle had been towing horses which were safely removed from the float.
He said there was nothing suspicious and believed the engine may have blown.