Chronically loosening lug nuts

TomT · Post by **TomT** » 18 Feb 2010, 13:00

I can't seem to keep lug nuts on the driver's rear wheel of a '94 945, even after resorting to an axle change. Something inside must be a tad loose because the rear end toe readings vary every time it is checked. I would have a tough time pinning this problem on spline or differential wear but I am running out of ideas.

Post by **JDS60R** » 18 Feb 2010, 13:29

I have seen this before on many different vehicles but most recently a new truck.
I recognize you replaced the drive axle but wonder if you did the bearing hub as well. The hub holds the threads and sometimes corrosion can wear them down. I have also seen where the overtightening of the lugs has bent the threads in the hub or on the bolts to where they are weak.

Best thing to do is replace the hub bearing and studs at one time.

I don't know why this is happening so much recently. Over the last 20 years I have only seen it 2-3 times. Now several times in the last few months alone. These all occured in different climates to. The truck was in Arizona and was only 6 months old.

TomT · Post by **TomT** » 18 Feb 2010, 21:12

I'm working on a rear-drive vehicle and the loosening problem is on the rear. The 'hub' is built into the rear axle which I replaced.

Post by **JDS60R** » 18 Feb 2010, 21:35

Tom

Sorry - I have had so many 850 questions lately I missed that you were on a 940 series.

Let me take a look at the axle and I will get right back to you

Post by **JDS60R** » 18 Feb 2010, 21:44

Tom,
Sorry for the previous mistake.

I have a few questions
Are your lug nuts the originals?
have you recently had the wheels painted or powdercoated?

TomT · Post by **TomT** » 18 Feb 2010, 22:19

No painting or powdercoating.
At one point, new oe studs and nuts were installed (different rim installed); things loosened anyway.
Next whole axle w/studs and nuts was replaced with a known good unit (another rim installed); things loosened anyway.
Shoot me!

Post by **JDS60R** » 18 Feb 2010, 23:37

Tom

That car owes you a six pack and you have earned it.
You have done everything I can think of. If the studs, nuts and wheel are matched to each other the normal torque should hold it without issue. Sometimes it comes down to lose powdercoating or paint but with a known good rim and new studs and nuts l am baffled.

Check the match of the nuts to the rim again. Perhaps the area of the rim where the nuts make contact is worn. Also take the rim out and make sure the studs aren't too long by putting a nut on and turning it down. See how far they go and if anything is caught inside the nut.

What torque are you applying?

After that if the torque wrench being used is accuate I would have to suggest a low torque anerobic threadlocker. Blue should be fine.

Post by **JDS60R** » 19 Feb 2010, 00:09

The threadlocker is only until this gets physically sorted. But its better to have them on then off while driving.

I think we need someone who has had this happen chime in.

The only issues I can think of are

1. Bad threads (worn, weak,corroded) this includes nut and stud
2. Small lug to rim seat/contact area (wrong lug, wheel worn at seat )
3. Wrong torque applied
4. Powdercoat or paint on wheels
5. Lug nut has something up in it and it is bottoming out so seat pressure is reduced
6. Studs too long producing low seat pressure
7. Mischeif - kids and late night pranks
8. Wheel has small fracture and is sepreating under torque of lugs
9. Corrosion on wheel to axle/hub mounting area too thick allowing wheel to come lose as it moves

TomT · Post by **TomT** » 19 Feb 2010, 06:29

I ceased to trust my clicker-style torque wrench also so I set 80 ft/lbs with my old pointer-type wrench.

Post by **cattledog** » 19 Feb 2010, 07:59

It sounds like you mentioned the most likely source of your problem in your first post.
The toe readings are different everytime they're checked?
If that rear knuckle assembly is rattling/ bouncing/shaking, as the vehicle is driven, albeit slightly, I'd think I'd be looking for worn bushings in the rear assembly , especially on that side and even more specifically on the toe adjustment link.
Just my $.02