I have experienced leaks from two different M46 transmissions. In both cases the gasket between the bell housing the the transmission developed a split in the gasket. In the picture you can see the break in gasket at the bottom of the transmission. In the other transmission the break in the gasket was at the top. If you have an aluminum case M46 you will need to measure and calculate the front bearing shim thickness. In both my transmissions, using the factory gasket let me re-use the shim which was in the transmission. I recommend buying the Volvo gasket instead of making one.