The ‘Big J6’ Specification:

20 to 22 ton G.V.W. six-wheeler, light duty.

Engine
V6 diesel, 170 B.H.P. at 2,600 R.P.M., maximum torque 370 lbs. ft. at 1,700 R.P.M., or AV 505 (right hand only) 170 B.H.P. at 2,400 R.P.M., or AV,471 (right hand only) 150 B.H.P. at 2,400 R.P.M.

Clutch
Single plate, cushioned drive.

Gearbox
5 speed constant mesh gearbox. Ratios: 1st 6.5 to 1; 2nd 4.49 to 1; 3rd 2.769 to 1; 4th 1.49 to 1; top 1 to 1.
A 6-speed constant mesh gearbox with under drive splitter could be offered on double drive V6 model.

Propeller shaft
1600 series universal joint with rubber mounted centre bearing.

Rear axle
Single drive bogie:
Single speed spiral bevel differential assembly. Ratio: 6.5:1. Fully floating hubs, or a 2-speed differential with electric shift, and ratios of 5.57:1 or 7.6:1. The trailing axle is made of composite construction with forged ends, butt welded to a tubular beam.

Double drive bogie:
Foremost axle: helical gear power divider incorporating air operated lockable third differential. Hypoid final drive. Rearmost axle: hypoid final drive. Ratios: 7.18 or 8.15 to 1.

Front axle
6½ tons capacity. Stub Axle 2.625 diameter. Axle beam section 4⅜" x 3⅛".

Steering
Re-circulatory ball type steering gear. 21" diameter steering wheel. Power steering an optional extra.

Suspension
Rear: 4 underslung semi-elliptic springs with balance bean carried on oil bath lubricated plain bush, fully protected from ingress of dirt. Springs: 50" cens.; 3½" wide; 11 leaves ½" Thick. Front springs: 54" long; 4" wide; 10 leaves; single rate. Telescopic shock absorbers on front axle only.

Frame
High yield strength steel side members. Section 12"x 3"x 0.28". Pressed steel cross members. Cross members and spring brackets attached to frame side members by high tensile bolts. Frame width 34" international standard.

Brakes
Cam brakes (leading and trailing shoe) with dual circuit full air operation. Front: 15½" diameter x 6" wide. Area=362 sq. ins. Rear: 15½" Diameter x 7" wide. Area=422 sq. ins. Single-pull air assisted hand brake, mechanically linked with rear brake cam shaft. Rear brake actuators of the triple diaphragm type.

Electrical
24 volt insulated return system of wiring. 35 amp alternator fitted as standard.

Fuel tank
Circular tank of 46 gallons capacity.

Cab
All steel welded construction with a forward entrance, and one piece screen of generous area giving good visibility. A shock absorber type driver and passenger seat, available as optional extra. A sleeper cab was also available on export models.

20 to 22 ton G.V.W. 6-wheeler, heavy duty, for towing a trailer (32 tons gross train weight). Specification as above, except for the following:

Engine
V6 diesel, 200 B.H.P. at 2,600 R.P.M., maximum torque 444 lbs. ft. at 1,700 R.P.M., or 6LX (right hand nnly), 150 B.H.P. at 1,700 R.P.M.

Clutch
16" diameter single plate, cushioned drive.

Gearbox
6-speed overdrive, constant mesh with 1.25 to 1 underdrive splitter box with air operated finger tip control as an optional extra. 6-speed Ratios: 1st 7.17 to 1; 2nd 4.45 to 1; 3rd 2.54 to 1; 4th 1.53 to 1; 5th 1 to 1; 6th 0.75 to 1. Ratios with splitter box: 8.95 to l; 7.17 to l; 5.6 to l; 4.45 to l; 3.17 to l; 2.54 to 1; 1.9 to 1; 1.53 to l;  1.25 to 1; 1 to 1; 0.75 to 1.

Propeller shaft
1700 series universal joint with rubber mounted centre bearing.

Rear axle
Single drive bogie:
Driving axle: spiral bevel with planetary hub reduction. Composite construction of axle casing. Fully floating hubs. Ratios: 7.69 to 1 (V6 200 with 6-speed gearbox); 6.35 to 1 (V6 200 with 12-speed gearbox or Gardner 6LX); 5.26 to 1 (Gardner 6 LX with splitter). Trailing axle of composite construction with forged ends butt welded to a tubular beam.

Double drive bogie:
Foremost axle: helical gear power divider incorporating air operated lockable third differential. Hypoid final drive, composite construction of axle casing. Rearmost axle: hypoid final drive. Composite construction of axle casing. Ratios: 5.97 (Gardner); 7.18 (V6 12-speed); 8.15 (V6 6-speed).