Here I show the modification to the 22G1128 gearbox case that allows running a full late A+ Gearset from a Rod-change transmission. The modification allows the case to accept the 3-step layshaft that is needed for the A+ style laygear. This is a viable option as most of the small input bearing mainshafts have passed into oblivion, and finding a good set of gears, particularly second gear in the pre A+ helical pattern is getting difficult… and expensive.
Running A+ (or even the large bearing “intermediate gears prior to the A+, including the close-ratio 1275GT type if you can find these) provides a number of upgrades to address weaknesses. Besides the stronger 3-step layshaft and gear, you get the larger input bearing mainshaft, and the corresponding stronger input gear. The later gears also have a different coating on the synchro cones of the gears which lets the baulk-rings (synchros) work better, and is more durable (it has a black, almost “soft” when oily texture compared to the shiny metal of early gears).
This is a great upgrade, as the early small bearing type were used on tiny engines, and take a real beating when asked to perform with big-bore engines making 4 or 5 times the power and torque.
Next, I’ll be installing the differential, then we’ll confirm our Idler-gear end-float.