I can't remember 100% but I think I just jammed the ring gear with a good screwdriver when I rebuilt the motor in th 380sel. Try hard not to damage the teeth though.
On the M103 there is a special tool you bolt to the trans that engages and jams the ring gear. Does such a tool exist for the M116?

__________________
Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi