80 series "4 studs that hold the steering arm on to the hub"

hi all,

l have recently had a problem with the 4 studs that hold the steering arm onto the hub (passenger side)

Background
My problem may of started last year when l hit a tree stump with the resultant (steering wheel was knocked out quarter of a turn) and the spindle that goes into the pitman arm was slightly twisted, all was ok, never the less l got a wheel alignment and all was to spec.

When we did the seals, both sides (wiper seal was shot) we noticed that the studs were either broken/sheared (l guess the tree stump hit caused this) so we replaced them and did up torc wrench tight.

It Was when driving on Monument Track (Vic high Country Dec 1, 2006) that the bloody studs had all fallen out/sheared/busted, bar 1. Ok, so we fixed that by using 2 from the other side, which got me to Mansfield and to a professional mechanic who replaced the 4 (passenger side). Cost $200. Well worth it l guess!
He (The Mechanic said these Studs dont break easily, infact he couldn't remember ever having to replace any and he'd been in the business for a guess 30years)

It wasn't until l was back in Melb about 6 weeks later that l noticed that the studs were coming loose again......OH. W.T.F. l have now replaced them again, used lock tight, Nylox nuts...and so far so good.

Does anyone have any suggestions or seen this problem before as lm trying to work out why it happen/what causes it, maybe what l should be looking for.

PS. l dont have a cracked housing and many people have said that you would not have elongated the stud holes as the steel is about 1" thick.

Thanks

Barn