Couple of Sixty questions

I went through the "Parts Catalog for Caterpillar Tractor Attachments" (form 309😎 for the Sixty, Sixty-Five and the Diesel Sixty-Five and could find no reference for a 7 spoke front idler.

Mr. Lorry Dunning had a comprehensive article on the progression of parts for the Sixty from the beginning to the end of production. I could find no reference to changes to a seven spoke idler.

The Sixty Tractor Parts Catalog (s) Forms 5451 and UE 5451 does not show and changes in the rear housings. I have noticed major difference between tractors. The innards appear to have stayed the same. There were many changes to the casting as the production continued

Your 7 spoke idlers may have been a transplant from a later tractor - maybe.

 [attachment=77398]IMG_8451.JPG[/attachment] [attachment=77399]IMG_8452.JPG[/attachment]Ryan Pickering might be able to help you on the info for the front idler changes. One of my parts books is showing a serial number break for the trani cases at 4118-A and PA-3853 with part number 1B2625 being used with and after these numbers and 1A1133 being used before these numbers back to 1126-A and PA-1. I am guessing that part number 1476-A subs to 1A1133. I do not know the differences between the two cases. What I have found with Cat is that a part number can have many running changes during its production run with those changes noted on the prints or the page that tells why the changes were made. An excellect example of a running change is the hood latch used on the 10, 15, 20, etc. It started as a mallable iron casting and it is now a pressed steel stamping. Same part number (T537) but different look.
Thanks
Ken

Ken, thank you for the two images of the rear tub, that looks like what I am seeing.  The 1926 tractor is just different than the others that Dad and I have, the first one that I bought is a 1928 but the others either don’t have serial numbers or have a mix match of different tags between the engine, tub or seat frame numbers. Thanks again, Mike 

The seven spoke idlers were standard on the Sixty-Five and Diesel 65. The reason they did not appear in the accessory book, is they were built with seven spoke and not an accessory (option). The Seven spoke would directly replace the original 5 spoke idler on a 60. NPR shows that eventually the standard 5 spoke was discontinued, and the seven spoke was shown as replacement.
The seven spoke is larger diameter, and requires 34 link track, five spoke used 33 link.
Form 5451 is the latest parts book, covers 2201A to 5532A and PA1 to PA 13516 easiest to find.
What are engine (motor) numbers on right side of block, and the engine frame numbers on left frame top behind radiator?