Chevrolet 1533X2 30-cwt trucks

[Tony Smith]

The Eaton 2 Speed diff was a very widely used diff in both military and commercial trucks from the 1930's right up to today. Methods of engaging the diff have ranged from a lever and solid rod, cable, pneumatic and electrical controls. During the war, they were fitted to Chev, Ford and Dodge vehicles in large numbers.

The adapter is a necessary part of the installation. The drive for the speedo cable, and therefore the speedo and odometer comes off the gearbox and is geared to read accurately when the diff is in the "High" ratio. When the "Low" diff ratio is selected, the gearbox drive will still be reading the higher speed for a certain gear/rev range. The adapter is switched with an actuating cable from the lever, and reduces the cable speed by a similar reduction ratio to the diff (which I understand is a reduction of 39%, ie a ratio of 1.39:1)

[Charlie Down]

To the rescue again Tony, thank you.

[Tony Smith]

Originally Posted by Tony Smith

The drive for the speedo cable, and therefore the speedo and odometer, comes off the gearbox .......

Note that I mentioned the Speedo Cable comes off the Gearbox, not the Transfer Case, like on all 4x4 CMPs and Marmon-Herringtons.

The 2-Speed rear axle was only ever fitted to 4x2 trucks, never 4x4s, as there would be a catastrophic speed difference between an engaged front axle and a rear diff in "Low" ratio. Catastrophic enough to blow up the Transfer Case. A 2-speed diff was never fitted to a front axle in any application I am aware of.

[Charlie Down]

I've put all the information I think is right to draw up a general arrangement for an LRDG 1533X2 cab. Not having one parked on my drive the dimensions will be estimates. However I am not aware of any drawings of the cab and most people base their knowledge on the Tamiya kit on the basis there is nothing better. So there are bits missing such as the gearstick, handbrake and 2 speed lever as I don't have any decent pictures of what the floor panel looks like and the levers would just get in the way of other detail. I intend to do a plan view drawing of the floor plate separately anyway, as well as side views. The steering wheel is also missing for clarity.
Any feedback, obvious cock ups, dimensions, drawings and photo's to help improve it would be appreciated.

[Charlie Down]

Just trying to confirm features on dashboard.
Any comments please.

[Tony Smith]

Originally Posted by Charlie Down

I've put all the information I think is right to draw up a general arrangement for an LRDG 1533X2 cab.

What is the square panel between the glovebox and leftmost gauges? I've not seen that in pics, and think the space in that gap should be closer and the whole dashboard narrower.

[Tony Smith]

As far as possible, the components on Canadian Chev (and Ford, Dodge, etc) were kept as standardised as possible and used across multiple vehicles.

Features on the dash are common with the detail pics of the Chev Cab 12 CMP components in THIS THREAD (although located in a different arrangement), and from that we can see the enamelled "GM Canada" dash jewel and the Inspection Light socket are also on the 1533X2 dash.

That thread will give you an indication of what the Ignition Switch, Choke and Throttle knobs should look like.

[Bob Carriere]

The current issue of the rectangular civilian instrument panel was a civilian style much like the first year it came out on trucks in 1940..... 1939 had the round gauges....... I would expect all of the original 38 or 39 Cairo modified LRDG to have been built with the round gauges....... round gauges may have been carried forward for the flat cowl conversion but would expect all 1942 factory 1533 to have the rectangular civilian style gauge cluster.

Lots of retro fitting and field modifications can be expected once the trucks saw action in North Africa......for example some of the factory rectangular folding windshields were removed, bumpers were dead weight...... at least half the waterfall grill was cut out...... and factory pictures do not show the huge water expansion tank on the driver's side.....spare(s) inside or outside the cargo box and I suspect machine gun mounts were field installed based on availability and ammo supply....... hard press to see two trucks similarly kitted side my each!!!!

In the various official messages reproduced on MLU of what they wanted never was it mentioned to have a 2 speed rear axle...... they made do with what they could get or scrounged from the battlefield.

That what makes them so interesting ......... the challenge is to make one that is plausible.

Cheers