Thread: Isuzu MSA Gearbox to LT230

Doubt i can get that it bicheno.
1 bolt to go and the handbrake cable and its out.
Hoping to leave it up there and just slide it back enough to get the shaft out/in

Unfortunately that shaft design shrieks of a lack of understanding of mechanical engineering. What you have is a gearbox mainshaft that is supported by two bearings inside the rear end of the gearbox and the end of the input shaft. With gear loading, especially in first, the shaft will flex ever so slightly. Now you've added an extension rigidly bolted to the rear and firmly supported by the transfer input gear and it can't flex like the original any more. Not only that but you can't rely on the absolute accuracy of the bolted joint to keep the shaft precisely straight. The point of maximum stress in the adaptor shaft would be exactly where it broke. Now you could make a new shaft that's thicker at the point of failure, as well as cutting the spline into shaft material at the OD of the spline, but it's still fighting the extra support in the transfer case. If you were really unlucky you'd break the end off the mainshaft where the output flange is attached.

What to do? In the short term, don't use first gear under load, use low range and third - fifth instead. There'll be much less flexing load on the adaptor shaft. Later you'll need a shaft with a flexible join to the output flange, not sure what the final answer will be but an engineering shop might provide a durable solution. A splined flange as shown earlier would be a definite improvement but keeping wear under control will be difficult. An actual universal/CV/rotoflex joint might work too, not sure if you'd have the room.