The bolt that has like splines all around it; what the hell do you do that up with without stripping it further

Situation:
Broke axles, got new ones, peice was left in diff, just removed diff to clean before fitting new axles and that bolt was completely undone

Don't know if that can cause damage

Need to finish this before lunch as i am towing a boat to the coast to go nab some tailor with some mates
