D2 4J series

I know that there are Caterpillar 3J and 5J D2s. But was there ever a 4J? It doesn't appear in the ACMOC serial number book, but I looked at a wrecked D2 this week and I'm sure the plate was 4J479 SP from memory. Was I seeing things? The owner thought it was a military model. Can the brains trust put my mind at ease?

The U series had a 5U (wide gauge) and 4U (narrow gauge). Was the air cleaner body behind the firewall by the operator or was it at the front right? JM

4J is an R2, same as the J series D2 except it has a gas engine.

That would explain it. All that was there was from the clutch back, no engine or front components and no track frames.

Hi cable control,

Josh is correct, 4Jxxxx is a narrow gauge R2.

Assuming the plate you mention was on the transmission case, then the tractor has been re-engined with a D3400 engine as used in the J series D2 tractors. If there is a serial number plate on the engine, it may start with 1Sxxxx, which would have been a generator power unit (if my memory serves me correctly).

Here in the UK, many R2 tractors were re-engined in this way.