I'll start by saying that this forum is wonderful! 
Just picked up 4G789. Both the pony and diesel seem to run well. 
It has a few issues that need addressing. The hydraulic control valve is stiff as can be. To raise the blade, I need to put a 3' pipe over the valve arm for leverage. The blade is a 4S blade (2A2044) which I am thinking is much newer than the tractor. Also,The right steering clutch lever is also very hard to pull. Once you get the lever to move, it steers fine. 
The service and operator manuals are supposed to arrive today. I'm sure that will be a big help. 
thank you for having me here! Jim. 

it appears to be a rd4 1936 year--check the blade valve linkage for binding--also the steering clutch linkage

Welcome, nice ole tractor.

Go easy on the that control linkage!!!!! What typically happens is the control shaft at the #44 unit drops down and binds the linkage inside the tank. Can cause some real damage to the linkage internally which has probably already occured.
 
 

Probably needs the hyd oil and filter changed anyway. Service manuals can be found on ebay, check the serial #'s

Welcome and congratulations, that's a nice looking tractor, and a early production run one too, 1936 was the first year of production, looking at your photo's the track frames have been replaced with track frames from a later model D4, like a 7J or 2T/5T, the top carrier rollers are different to the early RD4. 

You might have later model track frames, or someone fabricated a mount for the newer rollers, or someone dropped a RD4 motor and radiator onto a later transmission, have a look at the back of the tractor, on the left side there should be a second brass serial number tag, if it is a different number to the motor, let us know.

Either way, keep that in mind if you need parts for your track frames at a later date, just double check what you have there, before buying anything, because there are often subtle changes over models with things like track frame dirt guards and recoil spring mounts.

The RD4 are a nice tractor to drive, I use mine to disc fields every year, they really bark with a straight through exhaust! Remember to turn the gas off on the pony motor to stop it, don't use the ignition switch.
Good luck
Mike

Hi Tdozer3188,
welcome to the forum you have once looking Cat there, I see the OM has fixed you up the hyd control issue, as for your steering clutch lever there is a big retangle plate under the seat and there two cranks that have bearings that will be rusted solid as per my photos.

Hi Tdozer3188,
welcome to the forum you have once looking Cat there, I see the OM has fixed you up the hyd control issue, as for your steering clutch lever there is a big retangle plate under the seat and there two cranks that have bearings that will be rusted solid as per my photos.

  
 

regards

I pulled the cover off of the HCU. After disconnecting the rod that heads back to the operator station and disconnecting the spool from the vertical shaft that goes through the case. I found that the spool seems free and the linkage seems to be in place. That heavy vertical shaft seems to be froze up. 
As for the steering lever, I took the cover off at the base and found the hinge to be rusted. A little Weasel piss and working the lever, she's free!  
When the blade was installed, did they burn off the front carrier roller? The rollers do look like newer style. 

Well you lucked out on the #44 linkage, looks good, just make sure the roller stays centered in the float linkage.
You need a track adjustment as the sagging rails will cut right through the pivot shaft housing.

Track adjustment is on my list. It could use a set of rails. The bushings haven’t been turned, but quite a bit of internal wear.
I’ve changed the oil in both engines. The rest of the fluids are on my list too.