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