That hydraulic unit is a char-lynn unit from the late 50's early 60's. They were commonly used on the Redhead nut knockers and other early mech. harvesting equipment built durring the labor crunch in the early 60's. We even used those on our JD 40V and 420 high crop to provide hydraulics to run orbital motors on our bean cutters and vine trimers. I'll have to dig through the paperwork next time I am out at the ranch to get you a copy of the specs on the unit.

Funny thing is I was going to use one of those for the hydraulics, as we had pallets of them laying around at the time when I built by D4, but I was worried that connecting the pump directly to the engine would spin it too fast.

The hydraulic unit is called a Char-Lynn Hi-Lo-PAC

That was a common way for hydraulics back in the days when they werent
on every tractor. We have 1 or2 at our farm. Jason

Thanks all for the info, & Matt for the 'Dummies guide to S/Ns'

OM- Why would they not use USN?

Was the R4 a gov spec tractors like the R2?

CS

My Navy day memories are pretty rusty but as I recall the 7th Fleet was the Pacific theater and maybe the designation meant something instead of generic USN???

As part of the war production everything was government spec.

OM & Carl - FYI - The U.S. 7th Fleet was formed on March 15, 1943 in Brisbane, Australia, during World War II. It served in the South West Pacific Area (SWPA) under General Douglas MacArthur, and the 7th Fleet commander also served as commander of Allied naval forces in the SWPA.

Most of the ships of the Royal Australian Navy were also part of the fleet during 1943–45. The 7th Fleet formed a large part of the Allied forces at the Battle of Leyte Gulf, October 1944, which is often said to have been the largest naval battle in history. After the end of the war, the 7th Fleet relocated to Japan.

The reason that US7 .. rather than the generic USN .. is used to ID the U.S. 7th Fleet equipment, is because the U.S. 7th Fleet was a combined operational arm of the USN, that operated ..
1. Aircraft ..
2. A Taskforce ..
3. A Service Force (which supplied all the troops under the US 7th Fleet command with all their supplies) ..
4. An Amphibious Force.

The U.S. 7th Fleet was therefore regarded as a separate entity to the U.S. Navy, despite being under U.S.N. overall command.
The affectionate nickname for the U.S. 7th Fleet, during WW2, was "MacArthurs Navy".

There are substantial amounts of earthmoving equipment in the SW Pacific nations, that still wear the 'US7' stamp from WW2.
Some would have been sold off as war surplus, but some would have also been recovered after the War, when it was abandoned by the returning troops.

Some items obviously have been sold as military surplus, post-WW2, wearing the US7 stamp .. as the U.S. Seventh Fleet moved to Japan after WW2, and then spread to Guam as well.
The U.S. Seventh Fleet is still a very active USN arm, with a sizeable amount of the USN spread out around the SE Asian region.
I don't think they would possess the same amount of earthmoving equipment today, as they did during WW2, as their operations nowadays are a lot more airstrike oriented, rather than the island hopping amphibious assaults of WW2.

Today, they are effectively a front-line force, kept in that SE Asian area, to avoid the need to spend many days steaming from the U.S., to trouble areas that might erupt without warning.

U.S. 7th Fleet history .. www.c7f.navy.mil/Pages/history.html

Hi Oz,
Thanks for the history lesson:D
I was part of the 7th Fleet......and don't recall all that.
Some memories are better off lost;)

The R4 tractor had the serial number mounted on the left hand side of the tractor arm rest . the rusty section approx 5" x 4" had a cast iron plate fixed in position. it gave the serial number and year made, and the machine weight. S/N should also be on a steel tag on the rear transmiision to the left of the PTO plate. It should begin with 6G xxxx SP. I have a similar one 6G 4897 mfg 12/17/43. also have a spare engine stamped US7.
The R4 commenced as the Thirty 6G in 1935 - 1938, rebadged R4 1938 - 1944 ending in number 6G 5383. It should be the same tranmission and Fd as the RD4 4G.