My father has two RD-6s for sale, although one may be an early D-6.

The one with the RD-6 tag (lower bottom side of radiator) is a 3 cyl diesel and is basically a parts machine as the right final drive outboard bearing is shot and its rails and pads were removed and used on the other machine. It has a dynamo/generator mounted on the front left of the diesel engine but no lights. It has a rear mounted hydraulic pump and the blade lift cylinders, arms and controls are still there but the blade is gone. Upper rollers are decent and still turn. It also has a swinging drawbar on the rear beneath the hydro pump.

The other machine looks identical but the metal tag on the lower left side of the radiator appears to say D-6, not sure why. It is also a 3 cyl diesel. This is a complete machine and was operating up until 1983 when it was put in storage and a restoration started. The hood, fuel tank and instruments are off of it right now but otherwise it is still assembled and rolls freely. It has a front mounted hydraulic pump and has the hydro controls, lift cylinders and blade.

Dad had Alban tractor out to look at them 10+ years ago and from what he can recall, the Alban guy said they were 1935 RD-6s and were orginally sold to the Army. Not sure if that is accurate or not.

Looking for $2,800 for the parts machine and $5,200 for the other machine. I can get measurements for the pins, rails and pads if anyone is interested in that information. If someone can tell me where the serial #s are located, I can get those as well.

Thanks for looking.

This can get a little confusing, but technically neither one looks like the "RD-6" model, they both look to have all the design upgrades that came with the "D-6" designation. I'll explain - they are essentially the same basic machine as an RD-6, still even carry the same 2H serial number prefix but the curved-out steering clutch levers, cast iron gearshift quadrants, and smaller forged body injection pumps that are on these machines makes them appear to be the later D6 version of the 2H series tractors, which would put their serial numbers somewhere in the 2H3248 to 2H8966 range meaning they would have been built anywhere from 1937 to 1941. Now when the official changeover from "RD-6" to "D-6" happened in mid 1937, there may have been a few of the very early "D-6's" that still could have had the "RD-6" badges put on the radiators because Cat liked to use up all of the existing components it still had on the assembly line before utilizing the "fresh" components that were made for the model designation change. There are also a few other tractor models in the Caterpillar line where little confusing details like this are know to have popped up around the time of a model designation change, because of the desire to use up existing stock rather than scrapping otherwise good components. It's possible that you may have one of those tractors here, depending how close the serial number is to the changeover - or it could also have just had the radiator replaced with that off an actual RD-6 too, which would also explain it.

There should be two serial number tags on each machine, one on the back end just inboard of the LH drawbar bracket (one tag can be seen in the picture of the machine with no tracks and rear mounted pump) and another on the LH side of the engine block, ahead of the pony motor and above the oil pan mounting flange. Both of the tags on each machine should have the same number stamped on them, if the numbers are different between the tag on the engine and the tag on the rear end then that would indicate an engine swap was done at one point. If you can verify the numbers on both of the machines then we could pin down their exact years.

Also listing your location will go a long way towards getting interested buyers, since these things are heavy and don't move very easily people will want to know right away how much distance there is between them and your tractors. Good luck with your sale, I hope they find a good home.

I'm sure others here would agree with my opinion that scrap value should suffice. Not trying to rain on your parade, but it would be cheaper to buy a running unit. You could get more out of them by parting good tidbits and scrapping the rest.

Hello Sasquatch

Thanks for the additional information on the RD-6 to D-6 differences, that was very helpful. I hadn't thought of a radiator swap but that makes sense as a possibility. The use of the remaining stock of components by Cat also makes sense. I have a 1990 Case IH 685XL cab tractor that has some 695 components (they transitioned in 90/91) so I guess manufacturers were still doing that at least up into the 90's.

Thanks for the serial # locations. I will check both the serial #s on Tuesday and post that information.

Also, thanks for pointing out the missing location information. I thought I had put that in when I registered but must have missed something. They are located on my parent's farm in Greencastle Pennsylvania about 5 miles off of Interstate 81 at the PA-MD line.

Hello Stephen,

Thanks for the suggestion about parting them out and scrapping the remainder. Realistically you are probably right, parting out/scrapping probably makes more sense (Dad has gotten some prices to scrap them out), but sentimentally, we would like to see the one running again.

We have talked about putting the good one back together and getting it running but as always, time is the issue. We also realize that a running unit would be much more attractive to a buyer.

The best scenario might be to part out and scrap the trackless unit and then get the other unit back together and running. I'll talk to Dad again. Maybe he'll change his mind on trying to get her running.

Don't be in a big hurry to call the scrapper. Then they will end up in China. You will come out far better financially if you keep them listed here and offer parts off of them. You can always scrap what left after the good parts are going to collectors that can use them.

And I like your idea of making one from two and getting one running. Good luck.

Crine, I sent you a PM

I have sent you a PM regarding parts from RD6
Pete L.

that outside machine is interesting. it has thirtyfive, forty or RD6 style upper track carrier rollers. also has the mammoth injection pump! the only thing I see as the late 2H D6 is the gated shift lever and the badge on the radiator side. I have seen cast brass badges that read RD6 rather then the stamped D6 plates. the seat on that tractor is not from this world either? it overlaps onto the fenders.

Actually it looks like the smaller injection pump, with the forged body injector pumps just like the machine sitting inside. Also note the absence of the curved governor control lever that would be attached to the side of the flyweight housing just forward of the injection pump if it were the early big style, this machine just has the plug installed in that bore further indicating it's the later style. Also both machines have the gated shift tower and the curved out steering clutch levers, which were added to provide clearance for the shifter lever because of the wider gate of the later style housing. As I stated earlier, they both look like the later style too me, other than the early style carrier rollers as was pointed out.