Cat D2 serial number help

"SP" typically means "Specail Parts" had been added at the Factory.
What does that entail?
Good question because everyone has an opinion on this subject!
Most people agree that it was a specification change in the gearing as an Agricultural tractor typically has different speed requirements than a Construction or Logging machine.
Other people say that it includes Lighting Groups and Generators, Starting systems, PTO's and Hydraulic Pumps or Cold Weather kits. Although it is an accepted fact that most external options were installed at the Dealerships as per Customer specifications.
As far as build records on the D2's, I believe the common answer to that is No, none were kept at the Factory.
If this machine is disaasembled and scattered as you state. The best thing to do is study the J series machines via actually looking at several and or photographs to get some idea of what you are searching for.
Good Luck on your Aquisition!

Doubleclutch

Here's what Caterpillar had to say about the lettes after the S/N.

SP= Special parts

“SP” stamped at the end of the Serial Number indicates special parts were substituted for standard parts on the machine. Examples include special transmission gears, oversized idlers in place of standard idlers, and other items that required special attention on the assembly line, usually “deep” in the machine. “SP” was not used for add-on accessories such as lights, cab, PTOs, crankcase guards, and mufflers.

One should note on the older D8’s and some older D7's I think. The letters SP apply to any change of the standard transmission and finial drive gears there should be additional letters stamped on the right hand corner at the top of the bevel gear case, reading as such SPC-G. Formerly these numbers were stamped on the vertical surface just below the right hand of the bevel gear case. Although these markings do not indicate the type of special gears, they do afford an opportunity to check the original gears installed in the machine to insure against replacement with standard gears.

There was, later changes in the transmission and final drives as to the special parts.

Thanks drujinin and Kelly for the info

Here are some pics of my recent "project" that sounds similar to yours.
Hope they help. As you can tell, my was an "orchard worker".
brian

I have the following 5U's available to purchase; Sere. #4258, 5486, 8539, 9141. Can someone tell me what years these Cats were manufactured? None are direct electric start all have electric start for the pony motor. Thanks guys.