Regret unable to give you the serial number(can't find it!!!) Any hints where to look? Plenty of paint etc to shift.
Thanks, Bob

They don't give any info on tag location but from the pictures of the "R" unit the tag is right in the middle of the rear diamond shape support plate. Right where it is sure to get knocked off:rolleyes: Don't know if it is stamped elsewhere or not. Guess you'll find out when you open it up. There are variations in construction but basically similar unless your replacing parts.

ozdicko - Your LeTourneau PCU is a Model "N", and specifically, a Model "N4", as it is fitted to the D4. This PCU is a lighter version of the Model "R" .. as OM correctly notes, the Model "R" was only fitted to the Cat D6, D7 and D8. The Model "N" appears to have superseded the earlier Model "AN".

The Model "N" was produced from 1935, and ran right through to the end of production in the late 1950's, under LeTourneau-Westinghouse ownership.

The Model "N" was available in double drum and single drum, as were the Model "R" and Model "T". The single drum setups were specifically for operation with a blade only.
Your PCU is even more "barebone", in that it doesn't even have a fairlead setup above the drum. The fairlead arrangement was for the operation of towed equipment, or for operation where the cable was routed along the side of the tractor, rather than overhead.

The elbow at the top left of the PCU is a filler elbow (I can't figure why it's pointing downwards, unless it's to prevent water ingress) .. the bottom two plugs are oil level and oil drain plugs, in order from top to bottom.

The Model "R" and Model "T" were probably more common than the Model "N" .. and the Model "R" appears to have been the largest produced model of all the LeTourneau PCU's.

The number of LeTourneau PCU models is quite large. The models comprise the following versions ..

Model "R"
Model "R-678" (this was a wartime Model "R" with a predrilled neck that fitted the D6, the D7 and the D8 without need for any neck changeover if swapping from one model of tractor to another)
Model "AN"
Model "N" (with Models "HN" and "DN" as associated models - the "DN" was the 4 drum model)
Model "G"
Model "FG" (front mounted)
Model "NF"
Model "GH"
Model "FGH" (front mounted)
Model "FTD" (front mounted)
Model "AD" (front mounted)
The sales literature states the model used in the "super-imposed" version, as shown above is the Model "HN".

All the LeTourneau PCU's operate on basically the same principle - a simple straight driveshaft with a pinion on its end, driving bull gears, that are coupled to cone clutches .. with a simple, spring-loaded band brake, braking mechanism wrapped around the cable drum.

The models "R", "N" and "FTD" share the same drive principle as above .. but the Models "T", "GH" and "FGH" are slightly different .. in that they contain an intermediate gear, that is in contact with the bullgear, effectively being a double reduction drive arrangement.

Your D4, S/N 7J9941 was the second tractor off the assembly line in 1943, and it's a toss-up whether your LeTourneau attachments (blade and PCU) were built in a U.S. LeTourneau factory (either Peoria or Stockton), or at the Rydalmere (N.S.W.) factory in Australia.
The other two LeTourneau factories at Toccoa, GA, and Vicksburg MS, never produced PCU's during WW2.

There is a high likelihood that your tractor came directly to Australia fully equipped, from America.
The Rydalmere factory produced Carryalls, Rooters, Cranes, PCU's and blades from July 1941, and it had tripled in size by the end of WW2 to become the largest manufacturing facility in the Southern Hemisphere. This factory supplied a high proportion of LeTourneau earthmoving equipment used by the Allied Forces (both U.S. and Australian) in Australia and the near S.W. Pacific Islands.

If you look closely at the steel sections used in your attachments, you may be lucky enough to find either "USS" or "BHP" stamped intermittently in the steel surfaces.
This marking stands proud of the steel (not stamped into it), and is easily seen. "USS" stands for United States Steel (Co) and will ID it as U.S. made.
If the steel has the "BHP" marking standing proud of the steel section, it is Australian steel, and the attachment was built in Australia.

Interestingly, the BHP steel sections were formed to different section sizes as compared to the U.S. steel sections, and the LeTourneau plans had to be hurriedly re-written during late 1941, to accomodate the different Australian steel section sizes. As a result, all Australian built LeTourneau attachments have slightly different steel dimensions to the U.S. built units.

I am just organising to send you, your copy of the LeTourneau PCU operations and repair manual that you ordered. I'll include the "N" series parts book, it has useful info for you as well.

Interestingly, the Model "N" series was later produced (early 1940's to late 1950's) to fit a wide range of other brands of tractors, which included Allis Chalmers, International, Cletrac, Fiat and Vender.
These models all used the basic Model "N" PCU, but used a different adaptor ("neck" in LeTourneau-speak) to fit the PCU up to the particular make and model of tractor.

Re the "US7" stamp - this marking ID's the tractor as a U.S. 7th fleet item. The U.S. 7th Fleet was a huge assortment of Naval equipment, comprising everything from aircraft carriers down to earthmoving equipment, that was operated under Gen Douglas MacArthurs command, out of Brisbane during WW2 (after the Japs chased MacArthur out of the Phillipines).
Do a search using "Macarthurs Navy" (as the U.S. 7th Fleet was nick-named) and you'll find many interesting items of info.

The U.S. 7th Fleet was the primary tool used in the island-hopping campaign of the Americans and Australians, during WW2, to drive the Japs back.
The Engineers and SeaBees were often the first ashore along with the infantry and Marines .. to destroy bunkers, build or repair airfields, and set up facilities for the troops and logistics that arrived later.

Your tractor may have seen some Island-hopping .. but it's more likely that it was used in the construction of the Alice Springs to Darwin highway, or in the construction of some of the 300 airfields that were built by Australians and Americans in Australia alone, during WW2.

After WW2, it would have been sold off as War surplus. As a U.S. 7th Fleet item, it would have been a purchased tractor, under the ownership of the U.S. Navy .. not a Lend-Lease item.
Any Lend-Lease equipment issued to the Allies, was usually destroyed at the end of the War, under orders from Washington, even if it was new.

Thanks mate, I'm in Perth at the moment and will give you a ring.
THANKS ,Bob.