The 1984–1991 diesel models were available in short wheelbase F70, long wheelbase F75 and F77 pickup. In 1989, the DL-series diesel engine underwent a number of changes including a timing belt replacing helical timing gears, rectangular headlamps and four-wheel drive engagement in high range using an electric switch via a vacuum pipe. The code for the naturally aspirated model changed from DL41 to DL42. Later an intercooled version of the turbodiesel engine became available, with power increasing to DIN or JIS. In 1991 the Rugger/Rocky switched to automatic locking hubs.