My Cat D73T crawler has a pony motor that has 3 levers and starter. Whereas my parts books donly shows 2 levers. Thank you John

3T4390-up had the high/low transmission.

What year does that equal.

What year did Cat start putting electric starter on their pony motors?

Look in the attachments index of your parts book, the two speed transmission and electric start for the pony shown there.

if its not shown your book might be for a earlier model. look on the cover it will state seriel 3xy123 and up or abc to 897 for reissues of the earlier books

Mid 1946

 
Dates of castings can be found on engine blocks, cylinder heads final drive casings etc.
This is a guide to decipher the casting codes.

N U M E R A L C O D
0 1 2 3 4 5 6 7 8 9
N = 0
U = 1
M = 2
E = 3
R = 4
A = 5
L = 6
C = 7 sometimes "K" was used (British )
O = 8
D = 9
If there are 6 letters on the casting it is the day, month and year that that piece was made.
e.g.
U would be 1 M would be 2 (12)
U would be 1, N would be 0 (10)
C would be 7,D would be 9 (79)
There are 6 letters so I would know the date is 12-10-79 or 12th Oct 1979
If it has 4 or 2 letters it would be month and year of manufacture