On all JOHN DEERe early/late model b styled tractors that had the 38 in rims should have size 10-38 rear tires or 11.2-38 is the replacement size for the 10-38's to be correct.
A John Deere 2040 had a rear tire size of 13.6-28
rear 20x8-8
Right side of engine on rear
The first place I'd check is on the rear of the tractor, somewhere above the PTO riveted onto the case rear of the tractor.
Front and Rear tires - 10 to 14 pounds for the soft tread turf tires.
The serial number on a John Deere 4960 tractor is typically located on the left side of the tractor frame, just above the left rear axle. It can also be found on a metal tag attached to the engine block. For precise identification, refer to the owner's manual or check with a John Deere dealer.
There is a bracket required for it.... Good luck finding one though
for traction
right rear of tractor, under right side remotes, has orange plastic top on it
To provide more traction.
Check the rear of the tractor above the PTO. I may be wrong so if it isn't there check on the engine for a plate w/ a number of a cast engine number which your John Deere dealer should be able to identify and tell you at least what year it is.
If they are regular tires and the tractor is 2wd they are 11.2-24 and 4wd they are 9.5-24 If they are turf tires and the tractor is 2 or 4wd they are 41x14.00-20