When Jeep Went Diesel

The 1961-68 Jeep CJ-5 Perkins Diesels

In 1960, if you were on of the very few Americans who wanted a diesel in a car, light truck or utility vehicle, you had few options beyond a swap. Then came Kaiser-Jeep. For the 1961 model year, Jeep took the extraordinary step of offering a Perkins diesel option for the CJ-5 and CJ-6. Given the practically non-existent market for light truck diesels here in the States, one could logically assume the intent was for export markets where the diesel was popular. That is born out by some brochures printed by the Export Division of Kaiser and some Perkins CJs are found overseas in various places. A surprising number were sold here.

Perkins in the USA

After it’s recent acquisition by Massey-Ferguson (1959), the North American arm of Perkins was no doubt hoping to expand markets here. Somewhere along the way, they hooked up with Kaiser-Jeep to supply automotive versions of Perkins 4.192 engines for use in four-wheel drive CJ-5 and CJ-6 Jeeps. In a detuned form, the 4.192 was already in use by Massey-Ferguson in certain versions of the MF-65 tractor… mainly the Mark 1 version built for the UK from ‘58 into 1960. While a few 4.192 powered MF-65 tractors found their way here, the US market MF-65 diesels primarily used the Perkins 4.203, IDI, which was a slightly larger and more powerful evolution of the design and appeared in 1960. It later evolved farther into a  direct-injection engine… but we’re getting ahead of ourselves. Check out Tractor Talk in this issue to see a 1962 Massey Ferguson tractor.

The Jeeps

The CJ-5 (81-inch wheelbase) had debuted for 1955 and the longer wheelbase CJ-6 (101-inch wheelbase) a short time later. They were the mainstays of Jeep’s Universal line. The diesel was an option in both, but not in the 4×2 DJ line nor any other Jeep product. The 62 horsepower diesel  could certainly have fit in other Jeeps of the day that used the Jeep gas four, the Utility Wagon and Pickup, as well as the Forward Control, but those models were on the way out when the Perkins debuted. The Perkins was a little small for the Gladiator pickup or the Wagoneer, but we’ll bet Perkins would have gladly sold them the six-cylinder 6.354 for those applications … and it would have been a nice fit.

Into 1965, the only other engine option for the CJ was the F134, and 134 cubic inch F-head gas four that made 72 horsepower at 4000 and 114-lbs-ft at 2000rpm. Starting in ‘65 was a 225 cubic inch V6 that made 155 ponies and 230 lbs-ft. and headlined the CJ and C101 models into the 1970s.  Balanced against the gas four, the 62 horse Perkins held up pretty well. With only a 3,000 rpm redline, it couldn’t match the engine speed of the gasser but it had gobs more torque. Drivers reported “similar” performance. Though we could not find it specified in the available documentation, we figure that had to come with a change in gearing.

Available period documentation says the diesels were equipped with axle ratios “suitable” for the diesel, but do not list a ratio. A 4.27:1 axle ratio was most common in civilian CJs of that era. Also available were 5.38, 4.88, 4.56, 4.27, 3.73 and 3.54:1 ratios. We’d guess 3.73:1 for the diesel but whatever was used, the end result was a 30 mpg CJ that could almost keep up with the gas four.

The Perkins option featured a larger 9.25-inch clutch but the rest of the powertrain was the same as the standard CJ according to the year of manufacture. Standard was the T90 3-speed manual with an optional 4-speed T98. The diesel pressed the T90 torque input limits but the T98 had a very comfortable reserve.

Exact production isn’t clear from research but the best numbers we have through 1968 show 1,156 CJ-5 diesels and 589 CJ-6s.  Though some sources list them into 1969, documentation does not back that up, with no diesel prefix CJs listed. Surprisingly, Perkins CJs are seen fairly often, even if they aren’t plentiful. Parts for the Perkins mill are still available and most of the rest of the Jeep is just like any other of the era. There are a few engine parts unique to the Jeep, such as the thermostat housing and bellhousing.

The diesel CJs had a special serial number prefix. From ’61-63, it was 57558 for the CJ-5 and 57758 for the CJ-6. From ’64-68 the prefixes were 8310 for the CJ-5 and 8410 for the CJ-6. The numerical sequence started at 10,001 for both and carried over until production stopped.

The Legacy

One of the common threads in the early days of diesel in light vehicles was a lack of suds. The Perkins Jeep came pretty close to breaking that stereotype. It was a big and torquey enough engine to offer a pretty good power to weight ratio in the CJ and it fit the platform easily. A higher revving diesel might have been more optimal but with the right gearing, a Perkins CJ was a more-than-respectable performer.