Tech Q&A - Chassis - Rear End


I recently disassembled a Model A differential for repair and found a very good 37 tooth ring gear. The pinion gear was missing so I do not know the ratio. I know the "Standard Ratio" of 3:78 to 1 has 9 and 34 teeth on the pinion and ring gear. Also the "high speed" ratio of 3:54 has 11 and 39 teeth on the pinion and ring gear. I don't recall ever seeing a 37 tooth ring gear but we counted three times. Do you know if the 11 tooth pinion will work or where I can get the correct pinion gear? -- Dave Bockman, Visalia, CA

In checking the Ford Service Bulletins, March 1929, page 327 it states:
"To simplify production of gears and pinions we have discontinued manufacture of the A-4209AR, gear and pinion, 10-37 ratio and will hereafter supply a 9-34 gear and pinion under part number A-4209AR. I believe that answers your question....I would guess swap meets would be the only source for the 10 tooth pinion. -- Lyle Meek, Technical Director



From Jim Schild's book Restorer's Model A Shop Manual, here is a table showing the different Model A leaf springs
and their application.

Part Number Leaves Application
A-5310-A 10 A chassis front (all body styles)
A-5310-B 12 A chassis front - special equipment after November 1930
A-5560--A 10 55A, 55B, 140A rear (straight ends on main leaf), 295A
A-5560--B 8 35A, 35B,45A-B-C, 50A, 50B, 68A, 68B, 180A, 190A
A-5560--C 7 (with spacer) 40A, 40B rear
A-5560--D 10 ,60A-B-C, 130B, 155A-B-C, 165A-B-C, 170A-B, 160A-B-C, 255A
A-5560--E 10 66A, 78A, 76A-B, 79A-B, 82A, 82B rear, 150A-B, 255A

To view the list of body codes, click here.

Last Updated: 04/02/2014