Gearing up for 2020

Gearing up for 2020 by Tony Meade

Read this as well  Further information

Our Club chairman, Peter Cook, has rebuilt several three wheeler gearboxes, and discovered that there are several combinations of gearbox components. Some of the problems that Club members have encountered have been the result of either incorrect components, or having been rebuilt incorrectly.

I remember that I rebuilt my first BSA gearbox about fifty years ago with many new/new old stock components, and had actually installed it into the chassis. After moving house or garage several times, I had been looking at a Parts List and the Club’s Factory Drawings that I had become custodian of and realised that I had failed to put the Thrust Washer on the Reverse Idler Gear Shaft. I had to strip the gearbox again to fit it. I can only wonder how people managed to rebuild the gearbox without a large size drawing, having to rely on the Parts List diagram (that was reduced from A0 size to about 7” x 4.5”) and perhaps a primitive photocopier. Since digitising the Factory Drawings, we have the DVDs that include every one of the Factory Drawings, and recently have produced sets of Laminated A3 prints based on the Parts List for every FWD model for which a Parts List was produced.

There are also the Workshop Manuals produced by the late Mike Scott-Coomber and updated by Ian Pinkney that deal with the methodology. These are all available from the Club’s Regalia Secretary, currently Jonathan Lines. The job title dates back to the very early days of the BSA Front Wheel Drive Club, and merchandise such as key rings, window transfers and metal badges to mount on the headlamp bar on some models, or reduce the radiator airflow by fixing to the radiator honeycomb!

Peter Cook contacted me recently to check through a table he was producing to try and demystify the different trike gearbox/gear combinations. It is very important to understand that the internals,- gears, shafts, selectors, clutch operating fork plates and oil scrolls/flingers are not all interchangeable, except as a complete set. I have added to Peter’s table after examining all of the Parts Lists and individual Factory Drawings of the three wheelers, and the early four wheelers, (T9, V9 (van), Peerless Coupe).

The Gearbox internals were all listed in Factory drawing DM380 covering the models from 1930 – 1933. The 1934 & 1935 Parts Lists show the same as 1933. I have added some extra information in the factory table to make it clear which part numbers listed are First, Second, Top & Reverse Gears.

























There is only one combination of gears for the 1930 – 1932 Trikes (also used on the 33-35 TW1 models & V9 Van). There are, however some drawings on the DVD that are marked as “special” for 1931, but are not in any Parts Lists or DM 380.These are:



Part No

No of Teeth


Layshaft Gear



Top Gear with straight cut teeth;

Layshaft Gear



2nd. Gear with straight cut teeth;

Mainshaft Gear



Sliding 2nd. & Top Gear (NOT marked as special, but it might go with the above)

Primary Gear



Straight Cut teeth.

Could these be for the FW32 four-wheeler, as it would be heavier than trike? I have made a point of showing these in case some turn up in spares.

I also noticed that there are two different reverse idler gears 35-4248 (35-9122 with bush) shown in the 1930 & 32 Parts Lists, and 35-4030 (35-9032 with bush) shown in 1933-35 Parts Lists. 35-4030 is identical apart from length of teeth being .030” shorter than 35-4248 (which is NOT stamped with part number), The teeth of the First/Reverse sliding gear are also shorter on the 33-35 models.

There are two different layshafts with the double helical primary gears, but only the one main shaft, and one set of double helical gears. The Low Ratio Silent Constant Mesh Gearbox was used on K & R chassis (Peerless & T9) and has a gearbox casing 35-4001 with slightly different lay shaft to main shaft centres.



35-4099, 35-4034 and 35-4047

Top & Second Main shaft Sliding Gears

35-4102, 35-4035 and 35-4044

First & Reverse Main shaft Sliding Gears

35-4147, 35-4038 and 35-4049

Second Gear straight cut Layshaft Gears


Top Gear straight cut Layshaft Gear


Top Gear double helical Layshaft Gear. (other motoring programs are available!)

I have taken a small section of the 1932 Engine & Gearbox drawing 35-9052 because it conveniently shows the number of teeth on all of the gears and can be easily related to the 1930 – 1932 models.

There are two sections from Factory Drawing 35-9110 showing the layout of the gear selectors and the Reverse Idler Pinion/Shaft. I have altered some of the drawings to maximise the magazine images for clarity.

Fortunately, identification of most of the gearbox components is made easier by having the Part Numbers shown in the table stamped on them, but we do also have the BSA factory drawings for them if confirmation is needed.


















Here is a new table just recieved

Total Page Visits: 2677 - Today Page Visits: 2