The spring for the reverse band looks very weak and short.
The band is new and "quick change" model, the hogshead is aluminium and RHD.
Can I change the spring without taking apart the pedal axle and the notch pin which looks very hard to remove ? How do you remove that pin ?
I would about bet the band is riding up on reverse drum lip. Try losing the spring as much as possible and see if band will slide toward reverse of tranny .You only need about 1/16 of an inch.
Remove the band nut and washer, slide the peddle and shaft out part way then take the old spring out, slide a new spring in place. Then slide the shaft back in and replace the washer and nut. Adjust the tension on the band and you are ready to go. Be sure to place rags in the tyranny to catch dropped parts! Be sure to count the rags in and out.
Phillip, you'll have to take the transmission cover off to replace that spring. Don't attempt to remove the pin. It's not necessary and it's impossible to install a new pin without removing the cover first.
It's right hand drive, you can't just remove the shaft and it will only move back as far as the cam will allow. The shaft is pinned to the cam like the low is on our left hand drive. The band ears are trapped between the ends and as long as they spring back with the cam when the pedal is released the springs are just along for the ride. The right hand drive I worked on, I cut the reverse and brake shafts and installed the newer stub shafts in the two places.
To remove the pin(s) the hogs head has to come off. The pins are driven in or out after the head is sheared off. Because it an aluminum hogs head you need support under the parts so you don't break the shaft boss off. I would suggest if you that route, you get the parts to update.
If the band is riding on the reverse drum lip, get it off and adjust your band. It might be ok without any more work at this time. In the future when you replace the linings I would then make the updates.