From 1961 to 1965, optional for the CJ-5 and CJ-6 was the British-made Perkins 192 cu in (2.3 L) Diesel I4 with 62 gross horsepower (46 gross kW) at 3000 rpm and 143 gross torque at 1350 rpm.
In 1965, Kaiser bought the casting rights to the Buick 225 cu in (3.7 L) V6 Dauntless and the CJ-5 and CJ-6 got a new engine with 155 hp (116 kW) supplementing the four-cylinder Willys Hurricane engine. A similar model, the Jeep DJ, was based on the CJ.
The company was sold to American Motors (AMC) in 1970, and the GM engine was retired after the 1971 model year. (GM's Buick division repurchased the engine tooling in the early 1970s which served as the powerplant in several GM vehicles.) The "Trac-Lok" limited-slip differential replaced the "Powr-Lok" in 1971.
American Motors began using their own engines in 1972. Replacing the Hurricane was the one-barrel 232 cu in (3.8 L) (except in California). Optional was a one-barrel 258 cu in (4.2 L) (standard in California). Also in 1972, AMC's 304 cu in (5.0 L) V8 engine became available in the same tune as a base V8 muscle car. To accommodate the new engines the fenders and hood were stretched 5 inches (127 mm) starting in 1972 and the wheelbase was stretched 3 inches (76 mm). Other drive train changes took place then as well, including the front axle becoming a full-floating Dana 30.
In 1976 the tub and frame were modified slightly from earlier versions. The windshield frame also changed meaning that tops from 1955 to 1975 will not fit a 1976-1983 CJ-5 and vice-versa.
In 1979, the standard engine became the 258 cu in (4.2 L) I6 that now featured a two-barrel carburetor.
From 1980 to 1983, the CJ-5 came standard with a "Hurricane"-branded version of the GM Iron Duke I4.
Early Tuxedo Park models were trim lines, but the Tuxedo Park Mark IV was claimed as a separate model than the other CJ series (marked in 1965 as the "Universal"), with more differences than past models. The Tuxedo Park Mark IV was an attempt to crack the mass market; it was, according to Jeep, “a new idea in sports cars ... the sportiest, most FUNctional car on the automotive scene.” It added to the standard CJ chrome bumpers, hood latches, gas cap, mirror, and tail lamp trim. 81 and 101 inch wheelbases were available, with a variety of convertible top and seat colors, and front bucket seats in “pleated British calf grain vinyl.” Sales of this model, introduced in 1965, were low.
In Australia, a unique variant of the CJ5/CJ6 was produced in limited numbers. In 1965, when the CJ was given the all-new Buick V6, Jeep saw the need for something similar in Australia. As such, they began to fit Falcon 6-cylinder engines to them at their Rocklea factory in Queensland. The jeep was fitted with an engine, pedal box and clutch/brake system corresponding to the equivalent Falcon at the time; i.e. a 1965 CJ5 would be fitted with 1965 Falcon engine/clutch components. When the Falcon received a hydraulic clutch system, so too did the Jeep. Combat 6 jeeps were also fitted with Australian Borg Warner differentials, and Borg Warner brand gearboxes. Unfortunately there is very little documentation about these jeeps, and often the only way to conclusively identify them is by owner history. Web page describing Jeep's presence in Australia, including the "Combat 6"