hello I have a d2 with a 1A serial number tag on the transmission but no tag on the engine. I am wondering what it is or why? Machine has a lot of odd things on it. Was used for pulling machinery at caterpillar plant i was told. mike

Ill take a pic of a D6 tonite and post it with a tag on rear above the ser.no. and its just a trans. group meaning its jusy got diff gears in trans. kinda like the SP was on older machines. On later machines the just added a ser.no tag for specail parts like trans groups

That d2 I have has only 1 tag right where the serial number tag should be. Also has a tag on one of the final drive cases. the tag is about 3 or 4 inches long and brass. Ill look at that number on it tonight. The 1a number is 1A172 no 3j or 5j or 4u or 5u numbers on machine. This machine came out of the Davenport, Iowa cat plant if this helps.?.? Has rubber pads on it also. Mike

It was 1966 that I was out to the Peoria factory to a school & they used smaller tractors like the D2 or D4s can,t remember which but they pulled wagons around with parts & supplies to all areas of the factory & boy they would travel with them too.I can,t just remember either but I believe they had rubber tracks too on them also.

As many have said, Cat used 1A numbers as asset ID tags for the Vehicle Research Department. If you look at Eric Orlemann's Caterpillar Chronicle, you will see 1A numbers painted on many of the experimental machines. That doesn't mean that experimental machines weren't also referred to by numbers like "X1", "X2", "EXP1", "EXP2", ect. The factory might stamp their machine "X1", but at places like the proving grounds that tests machines for multiple Cat factories, you could have a bunch of "X1" machines running around, so they needed their own numbering system. If an experimental machine shipped straight to the field for endurance, it might have kept it's "X1" tag, but if it spent time at the proving ground, it probably would have gotten a "1A" tag.

I looked back though my notes when I was looking through some old test reports. A test from January, 1947 on some "high-torque rise" D8's (2U's) mentions machines with 1A numbers ranging from the low 400's to upper 500's. Your chassis easily predates those, but that is the right range for your engine. I'm curious if you find that the engine hardware is a much newer vintage than the chassis. Then again, if the tractor was significantly rebuilt before it was sold, it could have a totally different vintage of hardware on it than when it was first assigned a 1A number. Hope this helps.

Here is the number. Mike

I had this discusion many times with a retired Family member that worked at Cat. The first time I toured the plant they still had the little railroad running around there taking parts to different areas. They had D-2's and D-4s. The fellow I was talking to told me when he first started there in the 50's they were using 10s, 15s, and 20s. He said the company had put electric starters on all these units. He used to push full size rail cars under a road way between plants. He told me that most of the time everything worked fine unless it got icy. Then you would go a ride backwards. As he put it. "Hugging the aircleaner as the railcars pushed the D-6 back through the tunnel."

Here are two pictures of my tractor. Thanks everyone for all of the replies, I've gotten some good information on my tractor. Does anyone have any idea on the value of something like this?

Mike, if you can, post a few more pictures of of your D2, #1A172. I often wondered what was done with all the "test" tractors, for a new model. Great topic! Thanks Bill