CHEVROLET TECHNICAL

CHEVROLET CMP PAGE

On this page, I have tried to include as much technical information on the Chevrolet CMP vehicles as possible. Should you have any information that you believe should be included here, please don't hesitate to email me.

MODEL IDENTIFICATION

(Click on blue letters for photos)

*MODEL*	*GM CHASSIS DESIGNATION*	*CAPACITY*	*DRIVE*	*WHEELBASE*
C8	8420	8 cwt	4 x 2	101"
*C8A*	8445	8 cwt	4 x 4	101"
*C8AX*	8448	8 cwt	4 x 4	101"
*C15*	8421	15 cwt	4 x 2	101"
*C15A*	8444	15 cwt	4 x 4	101"
*C30*	8441	30 cwt	4 x 4	134"
*C60S*	8442	3 ton	4 x 4	134"
*C60L*	8443	3 ton	4 x 4	158"
*C60X*	8660	3 ton	6 x 6	160"
*C-GT*	8440	F.A.T.	4 x 4	101"
*Fox*	*8446*	Armoured Car	4 x 4	101"
*Otter*	8447	Reconnaissance Car	4 x 4	101"
*C15TA*	8449	Armoured Truck	4 x 4	101"

Note: F.A.T. is a factory built Field Artillery Tractor chassis. Other manufacturers produced bodies for these vehicles. In Australia, General Motors-Holdens built C-GT gun tractors in both the No 8 and No 9 variants. You can learn more about these at Keith Webb's Old CMP Site

Apparently, there was no Chevrolet C60T equivalent to the Ford F60T semi-trailer prime mover or tractor. Chevrolet semi-trailer tractors were merely C60S or C60L trucks with their bodies removed and a semi trailer hitch fitted. Nor did there seem to be a Chevrolet equivalent of the Ford F602L and F602S two wheel drive trucks.

All C8A models were fitted with the van type body used by the Heavy Utility Personnel (HUP) and Heavy Utility Wireless (HUW), etc. The C8A Heavy Utility family were the only Canadian built CMPs that were built entirely in the one factory. There was also a model called the C8AX which was a 8 cwt 4 x 4 chassis fitted with a No 13 cab which apparently differed a little from the standard cabs, mainly in having smaller front mudguards to suit it's smaller 13" wheels. All of the C8AX variety was supplied to New Zealand where they were fitted with locally built trays or bodies. By all accounts, and despite it's single speed transfer case, the C8AX was a superb off road performer, it's abilities far exceeding the WC series Dodges which performed similar tasks for the other Allied armies in the South West Pacific theatre. The New Zealanders called the C8AX trucks, "Puddle Jumpers"

In Canada the 6X6 C60X was not badged as a Chevrolet. It was known by GM and the Canadian Army as the GM C60X. However, GM-H built C60Xs in Australia were badged as Chevrolets.

All Chevrolets had an identity plate similar to this attached to the top of the engine cover in the cab. This plate is from an Australian built vehicle, the model # WO1 stands for War Office type one which was a Truck, 15 cwt, GS (Aust), No 1 cargo. I am not certain if the delivery dates stamped on Australian built CMPs are for the date the vehicles basic kit was completed in Canada or when the vehicle was finally completed in Australia.

TECHNICAL DETAILS

VEHICLES WITH MODEL 216 ENGINE

C8, C8A, C8AX, C15, C15A, C30, C60S, C60L AND G-GT

*ENGINE SPECIFICATIONS*
TYPE	Overhead valve inline six cylinder
BORE	3.500"
STROKE	3.750"
DISPLACEMENT	216.5 cu in
COMPRESSION RATIO	6.25 to 1
BHP	85 @ 3400 rpm
TORQUE	170 ft lbs @ 1200 rpm
FIRING ORDER	1 5 3 6 2 4
INLET VALVE CLEARANCE	0.010" hot
EXHAUST VALVE CLEARANCE	0.020" hot
*TRANSMISSION*	Four speed non-syncromesh
TRANSFER CASE (C8A, C8AX, C15A)	Single speed part time 4 x 4.
TRANSFER CASE (ALL OTHER 4 X 4)	Dual range part time 4 x 4. High ratio 1 to 1, low ratio 1.87 to 1.
DIFFERENTIAL RATIO (C8)	9.41 to 1. See note below.
DIFFERENTIAL RATIO (C8A, C8AX, C15)	6.16 to 1. See note below.
DIFFERENTIAL RATIO (C15A)	6.5 to 1. See note below.
DIFFERENTIAL RATIO (ALL OTHER 4 X 4)	7.16 to 1. See note below.
*ELECTRICAL SYSTEM*	6 volt, negative earth.

Notes: C8A and C8AX vehicles have Clark spiral bevel differentials. I'm not sure what design differential is fitted to the C8. The C15 has a GM design hypoid drive differential which has a self locking feature according to the MB-C1 Maintenance Manual. The differential locks due to the design of the teeth on the side gears and is similar in operation to the early Detroit Locker 'ramp type' differential. All other vehicles have a GM design spiral bevel differential. Axles in all vehicles are full floating type.

TECHNICAL DETAILS

VEHICLES WITH GM MODEL 270 ENGINE

C60X , FOX, OTTER AND C15TA

*ENGINE SPECIFICATIONS*
TYPE	Overhead valve inline six cylinder
BORE	3.781"
STROKE	4.000"
DISPLACEMENT	269.5 cu in
BHP	106 @ 3000 RPM
TORQUE	222 FT LBS @ 1800 RPM

Notes: The 270 cubic inch engine used in these vehicles is the same US built engine as used in the US CCKW, DUKW etc vehicles. I am not certain but I believe that they used the US Clark four speed gearbox as well. I am still endeavouring to find out this and what differential ratios are used too.

Acknowledgments

I have got this information from the following sources:

Graeme Stephens and Bob Dimer of the Military Section of the Veteran Car Club of Western Australia. Brian Gough of Oshawa, Ontario, Canada and Brent Borschneck of Pilot Butte, Saskatchewan, Canada. Thanks guys.

Australian Military Equipment Profiles, Vol. 1, Field Artillery 1939-1945, Michael K Cecil, 1992. An excellent reference on the Australian CMP gun tractors. Unfortunately now out of print. The good news is that a revised edition is currently being prepared. I'll let you know when it is available.

Australian Military Equipment Profiles, Vol. 3, Australian Scout and Armoured Cars 1933 to 1945, Michael K Cecil, 1993. This is definitely recommended reading. Contains much general detail on Chevrolet CMP specifications as well as the scout and armoured vehicles.