Rear Driver side axle nut coming loose

Driver8 · 06-28-2004, 05:03 AM

I have 1987 911 Carrera that is used strictly for DE. Over the winter I replaced both the inner and outer CV boots on both the passagener and driver sided of the car. When I was removing the axle nuts I noticed the driver side took very little force to remove while the passenger side required an air gun. After replacing the boots I purchased two new nuts and torqued them to 250 foot pounds, and off to the track I went. On my fifth track day of the season, coming though to toe of the boot at The Glen I heard a strange rubbing noise, after pulling into the garage I found the axle nut on the drivers side rear had loosened and the wheel was rubbing against the fender. I put some loctite on the nut re torqued and went out for another run. Everything held together for the last run session. After the event I ordered two new nuts and torqued them to spec and headed back to The Glen a few weeks later, everything held together the first day but during the second run group of the second day the rear drivers side nut came loose again and the wheel started to rub against the fender.

1. I am wondering if any one has ever experienced anything like this, or has any idea why only the driver sided nut is coming loose.

2. The nuts are suppose to be a one time use nut, is it the same for the washer? And just what makes it a one time use?

Thank you for your help in advance.

A

jpachard · 06-28-2004, 05:18 AM

That torque is too low. It should be 339 ft/lbs. I'll double check my manual tonight.

Cheers, James

Jess · Jess's Garage

The same thing happened to me on my track car as well.

You need to check the stub-axle that the nut is threaded onto. In my case, it was streching at the point where the treads start. Each time I tightened it up, it streched a little more.

The result, for me, was that the stub axle snapped off and my wheel went with it.

Jess

Jim Sims · 06:07 AM

Probably time to replace the axles; I will conjecture that there is a fatigue crack in the axle that has reduced the cross-section to the point that when you tighten the nut, the yield strength of the remaining material is reached. It then permanently stretches the axle loosening the nut; a real possibility is that the axle will fracture and the wheel assembly will separate from the car.

See:
Blown engine may have SAVED me money!

Jim

Randy Webb · 06-28-2004, 09:53 AM

COnsidering the safety aspects involved, it would be wise to pull the axle, clean it off, and go over it with a magnifying glass. Then get it Magnafluxed if you don't see anything. Maybe just replace it depending on the cost and your paranoia level. This might be a good time to look at (carefully examine and test) the other one too.

The cause is one or more of the following: age, stresses from racing, etc., a part that was low-spec., corrosion, over-torquing (tho who has the enregy to do that, I don't know), or bombardment by a large number of neutrons....

Chuck Moreland · 06-28-2004, 11:05 AM

That nut should have a cotter pin through it. #25 below. How could it loosen?

Driver8 · 06-28-2004, 11:12 AM

Chuck,

The 87 does not have the cotter pin. I believe they stopped using the cotter pin in late 85 when they went to the 108mm axle.

Driver8 · 08-18-2004, 06:07 AM

Sorry for the delay in posting my findings. After tearing the drivers sided rear apart I had found the hub had broke into two pieces. (see attached illustration) The part of the hub that gets pressed into the rear bearing broke at the base of the hub. That part of the hub remained in the bearing and the part of the hub that contains the studs was only being held in place by the self locking drive shaft nut. So once I pulled the caliper off and removed the drive shaft the outer portion of the hub was in no way connected to the bearing. I was just wondering if anyone has seen or experienced this, or if anyone might know of a cause. Thanks in advance for your help.

Aaron

jpachard · 08-18-2004, 06:25 AM

I've seen this happen at the track. Comes from high loading on the hub. I carry a spare to every event now. You will need to get the old bearing out now and press in a new one. The torque I mentioned above(339 ft./lbs. ) is correct. Re torque the nut after a day or so of driving. Make sure you use a new nut since these are self locking and are a single use item. Porsche also up-reved the part so if you have the old flange style nut you will need to get the washer too along with the new nut. Let me know if you need any more help.

Cheers, James

Driver8 · 08-18-2004, 06:46 AM

Thanks James,

I did replace both drive shafts, rear wheel bearings, hubs, washers and self locking nuts. Since it is a self locking nut is it wise to retorque the nut once it has been torqued to sepc (339 ft lbs)

A

Joe Bob · Joe Bob's Garage

Call me paranoid....but I would consider retro fitting the axle nut to use the cotter pin....

jpachard · 08-18-2004, 06:58 AM

Quote:

Originally posted by mikez
Call me paranoid....but I would consider retro fitting the axle nut to use the cotter pin....

You can't since there is no hole in the later driveshafts plus the torque is very different. The Castelated nuts are not designed for that high a torque.

Cheers, James