Rear Cv bolts coming loose

[Uniquenthony]

Unsure if this is the right section. Please point me to the right area to ask if not.

Have a vy 2003 manual ss 5.7lt LS1. I am certain my diff is needing a rebuild. Heavy backlash and a whirring when just on throttle and loud clunk when putting power on the wheels and letting them off.

I had my CV shafts replaced about 12 months ago for too much Play. Without more than 5000 KMs driving I had the cv bolts come loose. I had them hung off by a breaker bar at a shop which I couldn't prove. Co workers said I needed new cv joints due to being ripped off which is fine so I replaced with new CV joints. So brand new CV joints from Repco $180+ each had them installed me and co worker I know we hung off them with the breaker bar and covered the bolts in Loctite. That was carried out in November 2019. The cat barely driven again wouldn't have surpassed 5000'kms. In March had car engine cammed 230/236 and hadn't driven car until August yet recently been under car (20/11/2020) and CV bolts almost completely out of shafts again for 3rd time. Yet previous time was brand new bolts covered in Loctite with brand new CV shafts and 2 people on a breaker bar and still rattled loose.

Has anyone else had this problem and why are mine coming loose.

I am thinking maybe the vibration/hum in diff causing vibration in diff. A coworker says maybe the pitch in the thread inside the diff is gone so there's play causing bolts to vibrate with the movement that's there when bolts are tight.

I need new rear cradle mount bushes but coworker says if they were the problem why hasn't the cradle mount bolts rattled loose.

Need some guidance please car is currently undriveable due to this constant issue with the bolts coming loose even with Loctite and new bolts can anyone confirm its the diff whirring/vibration or had a similar issue.

 

[ephect]

Haven't heard of this issue, but it does sound plausible with the vibration. The Loctite should have held thou.

Are the bolts loose at both ends or just the diff end? Are the 3 curved washes that service 2 bolts each installed?

 

[greenacc]

If they tighten up when you hang off them I doubt the threads are worn out. If they were badly worn the bolts would keep turning. Pull a bolt out and see what the thread looks like.
Best idea would be to get the diff sorted out since you already know it's got problems and see if that solves the CV problem too.

 

[_R_J_K_]

If you've got two guys hanging off a pole to tighten them up, I'd say it's totally possible that you're stretching/yielding the bolts, then them coming loose is just exacerbated by whatever other problems you've got on top of being stretched. The important thing for these bolts is how they deal with shear force from the two flanges, not necessarily how tightly they're done up (but, that's obviously important too).

IMHO, you should get new bolts and just do it up to what it says in the workshop manual and see if it happens again (although knowing Holden it's probably some stupidly unnecessarily high number). Have never seen anybody do up tailshafts, CV shafts, or diffs, with two people and a breaker bar then have them fail/loosen.

EDIT: so the manual I was reading (not the FSM) says these bolts should be torqued with Loctite 242 to 50nm (which is not a whole lot of effort) then turned an extra 60-75 degrees which is about 1/6 of a turn, so totally possible that you're overtightening these by a big way. Try find the actual Holden manual and see what it says.

 

[_R_J_K_]

You also say "covered" in Loctite, how much are you using and which one?

 

[Immortality]

I think you might be right, if they have been overtightened that much they may be stuffed and need replacement. I do them up with a allan key and a small pipe extension and I've not had them come loose.