The Anzani Iron Horse is fitted with a Ford 3 speed gearbox with reverse, It is the same gearbox as was fitted to some Ford cars at that time. Its 2nd and 3rd gear are synchronous .
On my tractor, both reverse and first gear were engaging , but second and third were not. On my last day out ploughing , I tried to engage these without success…….I pushed so hard on the gear lever trying to engage 2nd gear that I actually bent the long rod from the handlebar gear lever to the gearbox top lever , so it was time to investigate. When ploughing, you really only use first and reverse , but having 2nd and third are handy when moving idle for longer distances in the field.
There is a gear linkage from the gearbox top lever back to the operators position at the handlebars.
. Four bolts secure the gearbox top cover.
Gear assembly , as seen with top cover removed.
Gearbox top selector. The small fork selector engages 1st gear and reverse. The larger fork selector engages 2nd and 3 gear. Both of these selectors are retained in their in gear and neutral positions by sprung detents .
Short You Tube Video showing how a 1936 3 speed gearbox works. Good basic illustration . https://youtu.be/JOLtS4VUcvQ
Here’s a similar Ford Gearbox from 1939’s. See here more into on a gearbox refit of a small Ford Truck This covers fitting a 1939 similar 3 speed gearbox in a small Ford 1935 truck. https://www.35pickup.com/Transmission.html
The detents on both gear stick fork selectors retain the gears in the neutral position.
Reverse Gear Engaged
First Gear Engaged
Note the damage to the gear teeth. This is a result of grinding the gears when trying to engage first gear. ( If you can’t find them….grind them ) This will often occur if the springs in the centrifugal clutch have weakened, allowing the clutch to engage at lower revs than desired.
Second Gear Engaged
The synchroniser sleeve moves backwards into position to engage second gear. When the synchroniser sleeve engages 2nd gear , it can move back fully solid against the second gear without any issue.
Third Gear Engaged
The synchroniser sleeve moves forward to engage the Third gear. When the synchroniser sleeve moves forward to engage the third gear, its amount of travel is normally restricted by the gear fork selector……however, with the selector forks removed, it is free to move further forward, When it is moved fully forward, the sprung detent balls (6 ) are exposed and will pop out of position. You need to fit something (eg like a fork selector ) in the groove between the synchroniser sleeve and the third gear to limit its travel further forward to prevent this .
With the synchroniser sleeve moved fully backwards against second gear, it’s possible to see the sprung detent balls. In this position , the balls are still securely retained.
If you move the synchroniser sleeve fully forward against the third gear, the sprung detent balls are now fully exposed , so they will pop out of position.
This drawing shows the location of the springs and balls.
The following extract from a Ford service document details the 6 sprung detent balls ” This style was actually used for part of 1939 production and at least into 1940 production for the light trucks and commercial vehicles using the light duty transmission. This style used a hub with six steel balls and six matching springs, which rested in the hub (7108). These were surrounded by the 7106 sleeve, which had an axial groove machined into its center. As the sleeve was moved forward or backward by the shifter fork, it would center itself in the neutral position when midway between second and high gears “
It also details of later models of this gearbox moving to 3 balls , instead of 6. This was introduced in 1940 and utilizes the three steel balls, three small springs, and three steel inserts to provide the centering action of the synchro sleeve.”
So , based on the facts that this gearbox was engineered for much higher power applications than that required in the Anzani horse , and that Ford progressed to using 3 radial sprung detent balls instead of 6, I decided to reassemble it just using 3 sprung balls. This allows the sleeve to move much easier so should allow easier gear changes.
I used a cable tie to retain the 3 sprung balls in situ (every second hole ) . Once all 3 balls were in place , I tightened the cable tie and then slid the sleeve back into its central position. Using a jubilee clip would also have been a good option.
Here is an extract from “Service notes” on this gearbox
The synchronizer types with the springs and balls require some care when servicing. Be cautious when moving the synchro sleeve in an open transmission. If you move the sleeve by hand rather than with the shifter lever, you may move it beyond the normal range which could allow the steel balls to pop out. The 01A type has the 3 balls and you can probably catch them, but the B or 48 type has six balls under spring tension, and you will almost certainly see one or more fly out before you can see where they went! It is best to leave the synchro sleeve in the neutral position, and to remove the complete synchro assembly as a single unit. I highly recommend that either style is disassembled inside of a box with sides high enough to capture any stray balls and springs, or disassembled inside a shop rag. The B or 48 types with the six balls and springs will normally require some pressure to separate the hub from the sleeve, or use a soft hammer to tap the hub out from the sleeve (using a rag to catch the loose pieces).
To reassemble the B or 48 synchro, place the hub flat, and place a dab of grease in each of the six holes. Insert the small springs and balls into their greased pockets. Pick up the hub carefully and set it down into the sleeve, where the splines began to engage. The hub should slide into the sleeve to the point where the six balls are protruding from the sides and preventing the sleeve from moving any more. Now, place a 2″ worm-drive hose clamp around the hub, which should cover all the balls. Tighten the clamp snugly which should force the balls back into the hub pockets. Take a piece of wood (a short 2″ x 2″) and tap the hub down into the sleeve. You’ll be able to drive it down so the balls are now covered by the sleeve, but will have to remove the hose clamp before sliding the hub the rest of the way down.
With a new gasket cut , I was ready to pop back on the top plate and selector assembly.
There is a dipstick on the front corner of the gearbox. Oil may be filled through this hole. There is a drain plug in the bottom of the gearbox housing to drain the gear oil.
With the gearbox reassembled, and the linkage bar now straightened out and refitted , it is now easy to select all gears. I’m looking forward to driving down the field to the next ploughing plot in 2nd or 3rd gear, instead of much slower 1st.
The Gear linkage pivots on a bolt attached to the gear housing. The bolt is not fully inserted, but locked in position with a lock nut, so as to allow for some movement backwards and forward against a spring. Its correct positioning helps make selection of gears easy.
Below is an exploded view of a similar gearbox that was fitted to early Ford cars