The rear pair of wheels are coupled to {HEAD ~ the front pair} of wheels through {TAIL ~ a drive assembly} 
through
The rear pair of wheels are coupled to { HEAD ~ the front pair } of wheels through { TAIL ~ a drive assembly }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL