Servicemens Ref Book

The Form FEO30521 comes in several versions .. the original 30521 and the updated 30521-01 and 30521-02 .. and is the only SRB for the later D4 tractor chassis .. although it covers the D4 6U, 7U, 5T, 2T, 7J, and 4G series.

The earlier versions of the D4's SRB contained the combined engine and tractor chassis repair info in the one SRB .. and maybe seemed to be more comprehensive, because this SRB covered the whole tractor in one book.

After WW2, the SRB's were separated into engine and tractor chassis books, so you need both, to have a complete set of manuals.

The alternative is to try and find a Military Technical Manual (TM5) for the D4.
I'm not sure if the military produced any manuals for the later model D4's .. however they did produce them during WW2 for the earlier models of D4.
Some of the Military Manuals were composed merely of reprints of Cat literature .. and some were totally re-written. The re-written military TM5's are excellent manuals, and I consider them superior to the Cat SRB's.

Thanks Oz Dozer, That helps me alot!! I'll look around for the other pub's. Thanks again, quinq

You might try...
Caterpillar Legendary Service Literature
Midland Press Corp
5440 Corporate Park Drive
Davenport IA 52807
1-800-228-7821
fax 1-319-355-3690
They can reprint the manuals well back into the 1930's...in easier to read 8.5X11" format. With the original quality. Last checked they were about $50 each. Mine were excellent.
Hope this helps,
alan627b