Jeep CJ

Jeep CJ: which version to buy and why

The Jeep CJ was sold as one generation from 1966 to 1987, in SUV cabriolet form, with nine versions. There is no later generation to “step up” to, so the buying decision is entirely inside this list: gasoline versus diesel, four versus six versus eight cylinders, 3-speed versus 4-speed Manual, and 60 hp versus 150 hp.

The Jeep CJ was sold as one generation from 1966 to 1987, in SUV cabriolet form, with nine versions. There is no later generation to “step up” to, so the buying decision is entirely inside this list: gasoline versus diesel, four versus six versus eight cylinders, 3-speed versus 4-speed Manual, and 60 hp versus 150 hp. Every version is AWD, none has boost (No), ground clearance is 175 mm on all of them, and kerb weight, gross weight, tank size, wheel size, 0–100, mpg and CO2 are not measured. What you can compare is power, displacement, specific output, gearbox step count, and the two top-speed figures that exist.

Which Jeep CJ generation to choose

There is one generation (1966–1987), nine versions, body type SUV cabriolet. Restyling is not listed separately. A generation-to-generation comparison is not available: the catalogue does not record a second generation. The practical choice is which of the nine 1966–1987 versions matches the job.

Specs that actually differ between versions

Shared across all nine: AWD, Manual, No boost, dependent leaf-spring front and rear, drum front and drum rear, 175 mm ground clearance. Fuel is Gasoline on seven versions and Diesel on two.

Nm is not measured on every version.

Power per litre: what the extra displacement buys

Specific output (hp per litre of displacement) is the cleanest arithmetic on this table, because weight is not measured.

• 2.0 MT: 85 / 2.0 = 42.5 hp/L — highest specific output in the range.
• 2.5 MT (106 hp): 106 / 2.5 = 42.4 hp/L — essentially the same density as 2.0 MT, with 21 hp more (106 − 85).
• 3.7 MT: 150 / 3.7 ≈ 40.5 hp/L — almost as dense as the small fours, and the power leader.
• 2.5 MT (88 hp): 88 / 2.5 = 35.2 hp/L.
• 2.1 MT: 60 / 2.1 ≈ 28.6 hp/L — the denser of the two diesels.
• 3.8 MT: 100 / 3.8 ≈ 26.3 hp/L.
• 2.4 MT: 60 / 2.4 = 25.0 hp/L.
• 4.2 MT: 103 / 4.2 ≈ 24.5 hp/L.
• 5.0 MT: 121 / 5.0 = 24.2 hp/L — lowest specific output: 2.5 litres more than 2.5 MT (106 hp) for only 15 hp more (121 − 106).

The extra displacement does not buy a linear power gain. 3.8 MT (3800 cc, 100 hp) is 12 hp weaker than 2.5 MT (106 hp) (2500 cc) despite 1300 cc more. 4.2 MT (4200 cc, 103 hp) is 3 hp above 3.8 MT for 400 cc more — 103 − 100 = 3 hp. 5.0 MT (5000 cc, 121 hp) is 29 hp below 3.7 MT (3700 cc, 150 hp) despite 1300 cc more.

Power spread: 150 − 60 = 90 hp from the weakest (2.1 MT / 2.4 MT) to the strongest (3.7 MT). 3.7 MT is 44 hp above 5.0 MT (150 − 121) and 65 hp above the weaker 2.5 MT (150 − 88).

Two versions named 2.5 MT — do not mix them

The catalogue lists two 2.5 MT Gasoline Inline-4 cars. They are not interchangeable.

The 106 hp 2.5 MT is 18 / 88 ≈ 20% more power on the same 2500 cc, and it is the only four-cylinder with a measured top speed (135). The 88 hp 2.5 MT is one of only two 3-speed manuals in the whole range (the other is 3.7 MT). If the name on a listing is only “2.5 MT”, check horsepower: 88 versus 106 is the fork.

Gasoline four-cylinders: 2.0 MT vs both 2.5 MT

2.0 MT (85 hp, 2000 cc, 4 gears) versus weaker 2.5 MT (88 hp, 2500 cc, 3 gears): +3 hp for +500 cc, and you lose a gear (4 → 3). Specific output drops from 42.5 to 35.2 hp/L. The 88 hp 2.5 MT is a poor trade against 2.0 MT on these numbers.

2.0 MT versus stronger 2.5 MT (106 hp, 4 gears): +21 hp (25% more than 85), same 4-speed Manual, same AWD, same No boost. Displacement up 500 cc. This is the four-cylinder step that actually moves power.

Among Gasoline fours, 2.5 MT (106 hp) is the one to prefer unless you specifically want the smallest engine (2.0 MT, 85 hp, still 42.5 hp/L).

Gasoline six-cylinders: 3.7 MT vs 3.8 MT vs 4.2 MT

Three six-cylinder Gasoline versions, two layouts.

• 3.7 MT: 150 hp / 110 kW, 3700 cc, 6, V-shaped, Manual 3, AWD. Peak power of the entire CJ list.
• 3.8 MT: 100 hp / 74 kW, 3800 cc, 6, Inline, Manual 4, AWD.
• 4.2 MT: 103 hp / 76 kW, 4200 cc, 6, Inline, Manual 4, AWD.

3.7 MT versus 3.8 MT: 50 hp more (150 − 100) from 100 cc less displacement, but 3 gears instead of 4, and V-shaped instead of Inline. That is the largest power gap between any two neighbouring displacements.

3.8 MT versus 4.2 MT: +3 hp, +400 cc, same Inline 6, same 4-speed Manual. Specific output falls (26.3 → 24.5 hp/L). 4.2 MT does not earn its extra 400 cc on power.

If the goal is maximum hp, 3.7 MT is the only six that matters (150 hp). If the goal is a 4-speed Inline six, 3.8 MT (100 hp) and 4.2 MT (103 hp) are nearly the same car on output; 3.8 MT is the denser of the two.

The V8: 5.0 MT versus the rest

5.0 MT: 121 hp / 89 kW, 5000 cc, 8, V-shaped, Manual 4, AWD, No boost.

Against 3.7 MT: 29 hp less, 1300 cc more, 4 gears instead of 3. Cylinder count 8 versus 6. 5.0 MT is not the power king; 3.7 MT is.

Against 2.5 MT (106 hp): +15 hp for +2500 cc. Against 2.0 MT: +36 hp for +3000 cc. The V8’s specific output (24.2 hp/L) is the lowest of the nine.

Buy 5.0 MT only if the requirement is the 8-cylinder V-shaped layout itself. On horsepower-per-litre and on peak hp, it loses to 3.7 MT and is only modestly ahead of the 106 hp 2.5 MT.

Diesel: 2.1 MT vs 2.4 MT

Both 2.1 MT and 2.4 MT are Diesel, 4, Inline, No boost, Manual 4, AWD, 60 hp / 44 kW.

• Displacement: 2100 vs 2400 cc (+300 cc on 2.4 MT with zero extra hp).
• Specific output: 28.6 vs 25.0 hp/L — 2.1 MT is denser.
• Top speed: 2.1 MT is measured at 120; 2.4 MT top speed is not measured.

There is no power reason to take 2.4 MT over 2.1 MT. The only measured speed among diesels is 120 on 2.1 MT.

Diesel versus the weakest Gasoline four: 2.0 MT has 85 − 60 = 25 hp more than either diesel (42% more than 60). Diesel versus 3.7 MT: 150 − 60 = 90 hp gap.

Performance and economy (mpg)

0–100 is not measured on any version.

Top speed is measured on two versions only:

• 2.5 MT (106 hp): 135
• 2.1 MT: 120

Difference: 135 − 120 = 15. The other seven versions: top speed not measured.

City, highway and combined consumption: not measured on all nine. CO2: not measured. Eco class: not measured. You cannot rank mpg from this catalogue; do not infer it from displacement.

Dimensions and weight

Kerb weight: not measured (all nine). Gross weight: not measured. Tank: not measured. Wheel size: not measured. Ground clearance: 175 on every version — no version buys extra clearance.

Weight per horsepower cannot be calculated. Chassis specification does not separate the versions: dependent leaf spring front and rear, drum/drum, 175 mm, AWD.

Gearbox: 3-speed vs 4-speed Manual

Seven versions use Manual 4. Two use Manual 3:

• 2.5 MT (88 hp) — 88 hp
• 3.7 MT — 150 hp

The 3-speed is not a “weaker car” marker: it is fitted to both a mid-four and the most powerful engine. If you want four ratios, exclude those two (or accept 3.7 MT for the 150 hp). If you want the power peak, you accept 3 gears on 3.7 MT.

Which version to choose

If you want the most power: 3.7 MT — 150 hp / 110 kW, 3700 cc, Gasoline, 6, V-shaped, Manual 3, AWD. It beats 5.0 MT by 29 hp and the next Gasoline four (2.5 MT 106 hp) by 44 hp.

If you want the strongest four-cylinder with a 4-speed: 2.5 MT at 106 hp / 78 kW — not the 88 hp 2.5 MT. Same 2500 cc, +18 hp, +1 gear, top speed 135 (the highest measured figure in the data).

If you want the smallest Gasoline engine and the best hp/L: 2.0 MT — 85 hp, 2000 cc, 42.5 hp/L, Manual 4. Close specific output to the 106 hp 2.5 MT, 21 hp less.

If you want a 4-speed Inline six and do not need 150 hp: 3.8 MT (100 hp, 3800 cc) over 4.2 MT (103 hp, 4200 cc). The extra 400 cc on 4.2 MT returns 3 hp.

If you want eight cylinders: only 5.0 MT (121 hp, 5000 cc, V-shaped, Manual 4). Know that it is 29 hp down on 3.7 MT and last in hp/L (24.2).

If you want Diesel: 2.1 MT (60 hp, 2100 cc, top speed 120) over 2.4 MT (60 hp, 2400 cc, top speed not measured). Same power; smaller engine; only measured diesel speed.

Avoid confusing the two 2.5 MT cars. 88 hp / 3 gears versus 106 hp / 4 gears / 135 top speed. Same name, different car.

Do not choose on clearance, drive, brakes, suspension, weight or mpg. Clearance is 175 mm on all; drive is AWD on all; brakes are drum/drum on all; suspension is dependent leaf spring on all; weight, tank, wheels, 0–100 and consumption are not measured.

There is no second generation to buy instead. Production is 1966–1987, one generation, SUV cabriolet, nine versions. The decision is which of those nine matches power, cylinder layout and gear count — using the names exactly as listed: 2.0 MT, 2.5 MT (88 hp), 2.5 MT (106 hp), 3.7 MT, 3.8 MT, 4.2 MT, 5.0 MT, 2.1 MT, 2.4 MT.