Model A & B
Ford Garage
Rear Axle Gear Ratios
The following table shows the various Ford part numbers and gear ratios for the matched ring and pinion gear sets used on 1928 through 1934 Model A (103-1/2" WB) and Model B (106" WB) Ford car and commercial chassis, not trucks.
In some cases both an 'A' and a 'B' prefix part number are shown for a particular gear set. This is because the original Model A part was physically carried over into 1932 and later production usage, but with a new 'B' part number prefix and suffix assigned. The actual physical parts were identical and unchanged.
As a matter of Ford process, all Model A parts which were also used on the Model B were renumbered by Ford in 1932 with new prefixes, and starting with no suffix.
The 'AB' and 'ABF' prefixes were issued by Ford in very early 1932, and were quickly superseded by the typical 'B' and 'BF' prefixes.
The 'AF', 'ABF', and 'BF' prefix gear set ratios were used with the small bore, small displacement 14.9 HP (R.A.C.) engines produced by Ford Motor Company, Ltd. in England.
| Model A/B Ford Part Number(s) |
Pinion Teeth* |
Ring Teeth* |
Gear Ratio |
Usage Notes |
|---|---|---|---|---|
| Aftermarket | 12 | 39 | 3.25 : 1 | Replaces the 3.27 ratio. Easier to install in banjo than 3.27 set. Best suited for light cars, and/or flat terrain, and/or higher horsepower/torque engines. |
| Aftermarket | 11 | 36 | 3.27 : 1 | No longer available. Best suited for light cars, and/or flat terrain, and/or higher horsepower/torque engines. |
| Aftermarket | 11 | 39 | 3.54 : 1 (actually 3.55) |
This gear ratio was used in post-1934 Ford production in a V8 straddle-mounted pinion format, but is not found in Ford Parts Price Lists in a Model A or B format produced by Ford. This ratio has been available aftermarket for many years in a Model A/B format and is considered a "high speed" gear set. Best suited for light cars, and/or flat terrain, and/or higher horsepower/torque engines. |
| A-4209 | 10 | 37 | 3.70 : 1 | Early 1928 production usage non-threaded pinion and ring set format for use with the early production drive shaft that was threaded for the pinion bearing lock nuts.
|
| A-4209-AR | 9 | 34 | 3.78 : 1 | Early 1928 non-threaded pinion and ring set format for Service Replacement use with the early production drive shaft that was threaded for the pinion bearing lock nuts. |
| A-4209-B AB-4209-A B-4209-A |
9 | 34 | 3.78 : 1 | Typical production Model A and B threaded pinion and ring set.
|
| A-4209-D (printing error of A-4209-B) |
9 | 34 | 3.78 : 1 | D suffix part number appears only in the October 1929 US Parts Price List. Typographical/error subsequently corrected/updated/replaced by A-4209-B) |
| Aftermarket (?) | 11 | 42 | 3.82 : 1 | This gear ratio exists in early 1928 non-threaded pinion and ring set format, for use with the early production drive shaft that was threaded for the pinion bearing lock nuts. This ratio is not found in any (global) Ford Parts Price Lists that I have ever found, but apparently was produced as an aftermarket replacement at some point in history. |
| A-4209-C AB-4209-B B-4209-B |
9 | 37 | 4.11 : 1 | Typical production Model A and B threaded pinion and ring set.
|
| Part Number Unknown | 9 | 39 | 4.33 : 1 | This gear ratio in a Model A or B format is not found in any (global) Ford Parts Price Lists that I have ever found. (This ratio was in-fact produced in the later post-1934 production Ford V8 straddle-mounted pinion format, and does appear in Ford literature for those years.) Genuine Ford script Model A/B sets were produced, however, and actually do exist. I would appreciate seeing any Ford evidence identifying the Model A/B part numbers for the 4.33 set. |
Ford England 14.9 HP (R.A.C.) Gear Sets |
||||
| Model A/B Ford Part Number(s) |
Pinion Teeth* |
Ring Teeth* |
Gear Ratio |
Usage Notes |
| AF-4209-AR | 9 | 41 | 4.56 : 1 | Early 1928 non-threaded pinion and ring set for use with the early drive shaft that was threaded for the pinion bearing lock nuts.
|
| AF-4209-B ABF-4209 BF-4209 |
9 | 41 | 4.56 : 1 | Typical Production Model AF and BF threaded pinion and ring set.
|
| AF-4209-D (printing error of AF-4209-B) |
9 | 41 | 4.56 : 1 | D suffix part number appears briefly in some foreign Ford Parts Price Lists for use with 14.9 HP (R.A.C.) British Model AF Fords. Typographical/error subsequently corrected/updated/replaced by AF-4209-B) |
Current (2020) reproduction 3.54 and 3.78 ratio gear sets are made in Italy, and are missing the correct reduced diameter (slip-fit) on the front of the pinion where the forward Timkin bearing is placed!
The forward bearing will be quite difficult to install, and bearing preload will be very difficult to determine and set.
It has been reported that the offending gears ship in a fancy Motive Gears box. Inspect the pinion carefully. There should be a very slight step reduction in diameter between the two bearing positions.
Original Ford Ring and pinion gears were individually matched and lapped to each other for quiet operation on a Gleason Gear Lapping Machine, as shown and described in era Ford literature and Ford manufacturing articles.
NOS matched gear set pairs usually had a matching three digit serial number electrically or mechanically inscribed freehand somewhere on each gear.
Additionally, NOS gears usually have traces of orange lapping compound on the teeth. The compound was used during the matching/lapping process of the gear tooth contact. The orange lapping compound residue should not be mistaken for surface rust.
In some instances the original ring and pinion tooth count can also be found stamped on the banjo housing web or flange, as show above.
More related information on Ford Garage:
- For more Model A & B related information, use the Site Search box at the top or bottom of this page.
- Model A & B Original 5-Z-1833 and 5-Z-2065 Pinion Nut Wrenches
- Model A & B Drive Shaft Differences
- Model B Drive Shaft Removal Methods
- Model A & B Pinion Gear Race Removal Methods
- Model A Mitchell Synchronized Transmission
- Model A Ruckstell Dual High Transmission
- Model A & B F-150 TOD Transmission Conversion ~ Tremec T170FT RTS
April 2009