Hi all...I'm referring to the inner nut on the suspension ear ,inner end of pivot shaft.
Can anyone tell me why this nut always seems to loosen? Every time I put a wrench on it I can tighten it by about 1 turn. It tightens up, then a week later it's loose again?
Car is a 74 2.0 liter, I have Eric's bushings in the trailing arm.
Thanks!!
Mike

Have you changed the nut? It's a one-time-use nut. Kind of like a nylon nut, but without the nylon. Instead, the factory cut a tiny slot on the side of the nut. It's supposed to help the nut compress at different torque ranges and produce an effect similar to double nutting a bolt.

It probably has lost it's locking ability because it has been pulled off and put back on a number of times. Now, you can tighten it, but every time you drive the car the suspension is moving up and down. The 'up' movement would cause that nut to loosen (imagine looking at that nut straight on as the suspension is moving up and compressing the shock absorber, it would cause a lefty-loosey effect).

Hope that makes sense.

My guess is you didnt get it torqued properly. I have only had problems with them loosening when they haven't been tightened enough. I forget the spec but those things are supposed to be torqued down to something pretty ridiculous.

I checked the factory manual and the torque is 87-103 Ft Lb. I does not say to replace the nut. I have seen them get damaged and loose the locking properties. You should also look at the splines on the end of the pivot shaft. They may be worn smooth if the nut has repeatedly come loose. Have some one look at the outer end of the shaft to see if it is turning when you tighten the inner nut. The shaft may be turning and you would not be getting proper torque.

Bruce

Bruce...it does tighten, just doesn't stay tight.
With the heat exchangers I have no idea how I'd get a torque wrench on that!!
It's difficult to get ANY wrench on it.

Rob-O....Are you sure this is a one use nut?
What you are saying does make sense....

its a symptom of chassis ear flex
do you have wide sticky tires or drive under a lot of G-loads?

when we first started tracking... those nuts would come loose daily
next thing that happened is we ripped the console out

fixed it and ripped it out again, in a matter of a hundred miles.

the true solution are console braces.
those nuts never came loose again in 20 years once the bracing was installed.

brant

Please tell me more about console braces. Stock tires and wheels, mostly drive it like an old lady....mostly.

If you installed new bushing and didn't grind back the bushing to expose and make sure the serration on the pivot shaft engages the ear......it will get lose.

Did you do that when they were installed?

Pretty sure. I don't remember where I saw the information. If Bruce says it's not in the factory manual, then maybe it says it in the PET.

The shaft is not supposed to move. The bushings are supposed to move on the shaft.

I would suggest a dab of locktite and the proper torque to make sure it doesn't back off again.

If you got the hard replacement rubber bushings from PMB the bushing will sit "proud" of the control arm enough to be longer in OA length to the pivot shaft.

If you didn't grind them back to less than the pivot shaft length then the pivot shaft will have a hard time staying stationary relying just on the torque on the nut and the surface of the new bushing against the chassis mounting points.

The serrations of the pivot shaft end are intended to lock against the suspension ear and the outer mount near the side valance.

It could also be the "ear flex" but if you haven't done the above.....I doubt it.

Awesome....this means I get to pull it all apart again.
Excellent news....

Well.....IF.....you think that is the problem....why couldnt you just drop the front
of the control arm down and just grind the face of the bushings...measure the
OA against the pivot shaft? That way you don.t take everything apart

Just a thought.

According to the factory manual:
Control arm bearing on control arm.
Inside = 87 ft. lbs
Outside = 108 ft. lbs
Both Self-locking hex.nut
Threads M 14x1.5 Grade 8 G

Steve...thanks for the torque specs. Are you saying I should replace the nut?
Mike

914 teener...it's a good thought but with the heat exchangers just under the trailing arm, I would think that would be impossible. I can hardly get a box end wrench on it to tighten it!!
Mike

You can break the nut with the HE's on. I've done it. You may need to remove the shock IIRC. I used a box wrench and with the car jacked up high enough...wasn't much of a problem.

Then just break the three nuts on the mounting pedestal...remembering how many shims are there and in what positions.

Not sure if you need to just unmount the rear caliper and take off the e-brake cable with the one clip. I think you do.

You should then be able to muscle out the pivot shaft from the chassis ear.

Then just tap the pivot shaft through the bushings.

I just use locktite and tighten it as best I can. I have never had the inside one come loose. Only the outside when it wasn't torqued down. When it slipped it would make a klunking sound.

Here's a pic of what it should look like.

Click to view attachment

Common issue with Poly bushings on the rear. They are supposed to be trimmed so the metal is touching metal on the trailing not the bushing touching the suspension ear.

Interesting. I followed Eric's detailed instructions and there was no mention of trimming that part of the bushing. Regardless, I don't think I installed it incorrectly, I know that the end of the pivot shaft needs to lock into the suspension ear.
Something's going on here, but I'm not sure what!!!

Steve,

not challenging your input but can you explain how you can torque down one side with a different value than the other side?

How would you "hold" the axle without holding the other side with a wrench?

Thanks!

As I read the factory manual it gave a range of 87-103. The Porsche tech book did list inner and outer at different torques. Unless the engine is removed you aren't getting a torque wrench on the inner nut. Once the nut is snug the splines of the shaft keep it from turning.
Bruce

Exactly right Bruce...I don't see any way to torque the inner nut with the engine installed.
Mike

I was just out in my garage trying to remember if there was room because I have done it.

You can get an extension with a short socket on there with ease. It won't rotate but about 15 deg or so but you definitely can get a tool on there.

I don't know why you are saying the above. Just trying to help you.

Who knows why the torques are diferent, but pick up a manual and check for yourself. Interesting that the Haynes and Clymer manual say 50 on the inside and 108 on the outside. The Manuals are full of torque settings for bolts that you can't get to with a torque wrench. I use them as a guide and tighten the bolts any which way I can when a torque wrench won't fit.

914 teener...room up there for a socket, extension and a torque wrench?
Mike

Breaker bar and short socket....sorry.

Assuming the inside nut on the supension console.

I took the entire rear suspension off my car two years ago and rebuilt it


I did not take the engine out. I did a thread on it. Search is yourfriend.

I can get a box end wrench on it and tighten it in small increments.
Not a socket and torque wrench.
Mike