We just had to remove the GV "brain box" in my bro's 69 4speed Charger (518 Hemi), since it would pop out of OD with no warning. Dave at GV was helpful, but said it could be a RF issue or a voltage drop issue. Seems that if voltage goes below 12.7, it'll turn itself off & he said Optima batteries & stroker motors seem to draw more starting voltage, making that a problem. We have 2 Optimas in the trunk & one had the positive terminal come loose, which caused the problem...so we thought. After it happened again, we bypassed the GV brainbox & it seems to have fixed it...almost. But also seems a custom made shifter button (micro switch) that controls both the GV and the line lock may be causing it to go into OD on its own. SO, the next fix is to disconnect the line lock from the micro switch & switch to its own on/off switch in the ashtray.