I am thinking it is time to deal backwards detective work. I suggest beginning by comparing parts on the deck to the Deere dimensions. I would suggest measuring the dimensions on the pullies currently installed then look at what Deere calls for.
Here are the dimensions for the proper Deere pulley used on the idler and the tensioner:
Idler Pulley 4-3/8" OD, 4-1/8" flat Diameter, 3/4" flat width, 1" overall width, .669" bore- replaces John Deere AM107468 / AM37249
Also, Deere says the pullies on the spindles are 4" on the 39 deck. The larger pulley from a 47 deck will work on the same spindle so I would also suggest checking measurements on the spindle pullies. Also, swapping spindles from one deck to another is as simple as loosening 3 bolts. One more though - larger pullies on the spindles will slow blade speed on the smaller deck with shorter blades.
Also, noticed this between the older 39 and the newer 39,
Part # Serial range Length
M45998 - 176558 (A) DRIVE (39) 2.111 M (83.10")M47043 176559 - (A) DRIVE (39) 2.014 M (79.30")
Also, the Deere idler/tensioner pullies I have used were black since they were used on MULTIPLE applications (decks, snowblowers, etc)
One last thought - something makes me think the spindles and pullies were from a larger deck. They were used to replace the original spindles with bad bearings. I could be wrong...
Save the diagram I attached then print it for your reference.
Edited by Trav1s, November 09, 2013 - 10:46 AM.