bottom shock mount on C900 a-arms

Hi, put the front right shock back on it's mount on the a-arm on my 1985

900i today after replacing the balljoints and the tie-rod end.

Problem I have is that the nut to secure the shock to the a-arm won't torque up - it's really tight but it's turning like it's twisted off it's thread on the mount pin. The nut was threaded properly to begin with.

Any ideas? I don't want to replace the a-arm but since the car isn't going to be registered any time soon it might be alright just for local grunting (not on the road).

What makes it most likely to have stripped it's thread is that I can't get the nut off either! I guess the combination of a bit of rubber from the shock bushing with a little of the bush lube might be part of it.

Craig.

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Craig's Saab C900 Site
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Craig,

If you can get it off, maybe with some WD-40 or whatever penetrating stuff they might sell in the UK, get a tap and die the right size and clean up the threads before putting it back together.

Charles in Golden, CO

Reply to
Charles

WD-40 isn't a penetrating oil. It pretends to be, but for anything other than _W_ater _D_isplacement, it's a lousy compromise.

Craig, someone must have a lower a-arm. If the threads are stripped, for a shock, I'd rather replace the a-arm than to improvise.

Reply to
Dave Hinz

Yeah I know they're easy to get since there are a few European wreckers here in Sydney so there will be some C900's around waiting to be stripped. Getting new bushes is trivial. I'm surprised that the thread for the shock mount has appeared to have stripped so easily - I set my torque wrench to the right setting (around 60 ft/lb if I remember what I read in the Bentley book two days ago), and it would have got to about 40. The nut can't be removed with finger pressure and a spanner will turn it but it needs a fair degree of force. It's just not moving anywhere, though I guess there is some bush lube, etc. gunked into the thread otherwise I should have been able to see little bits of metal around the outer side of the nut where the thread of the 'bolt' on the a-arm comes out. hmmm

I'm hoping that the a-arm doesn't have to be replaced and just for a dudded thread it's a bit radical but since the lower shock mount is fairly important (!), that pushes it up the priority scale.

Craig.

PS. Photo's are still on the camera. 8-)

Reply to
Craig's Saab C900 Site

Well, that's a _very_ rust-inducing location right there. The nut probably got somewhat stripped last time it came off, which then munged the threads, which made the rust worse, ...

Well, at this point you've got nothing to lose by putting a deep socket and air-wrench on it, see if you can at least get it off that way so you can evaluate that thread.

Yeah, suspension is way up there in "things not to improvise". Or Improvize, even.

Reply to
Dave Hinz

WHAAAAAAAAT? Screams in astonishment.

That thread is about a 10mm thread (less?). There is no way you tighten a nut on 10mm thread to anything more than 20 ft/lb (add that I have no theoretical engineering background).

What is the size of the nut, circa 13mm?

60(ish)feet pounds are for roadwheel nuts.

You first have to get it off and then clean the threads and see the damage. From memory the nut only held the shocker in its natural resting place. It is not used to hold the A arm in place. A self locking nut (+ washer or whatever similar) should only need hand tight pressure. Torque setting is not given for that nut in the Haynes manual!!!

Could you be looking at some different torque settings?

if I remember what I read in the Bentley

Take it off first and come back.

I wonder, for internal threads there is an insert that can be used to rethread them. Would there be a similar sleeve to in effect rethread the bit in question. Rethreading (in effect) a bold will weaken it as it will be made thiner.

Hope it helps. Charles

Reply to
Charles C.

From memory I think it's a good deal bigger than that. Maybe closer to 19mm?

John

Reply to
John B

The nut could have a built in washer and be any odd size ... the thread though is important. But if bigger than 10mm then I am wrong :-D

Reply to
Charles C.

Page 731-4 in 8V Bentley C900 manual...

Tightening Torque for front shock absorber to lower control arm - 90 to 100 Nm (66 to 74 ft-lb). Seems quite high but it's quite a critical fastener.

Not sure off-hand.

Actually, the torque for those is specified as about the same range - 90 to

110 Nm (66 to 81 ft-lb).

That's correct re what the nut does. It pushes a big washer against one side of the shock lower mount bushing which holds the bottom of the shock in place on the a-arm.

I double-checked by looking in other places (such as the section on replacing balljoints) and the same numbers are quoted.

Well if I can get the nut back off againt without damaging anything else (mainly the shock bushing itself), I'll see what's happened and then work out what to do. Either get a replacement a-arm from a wrecker, or see if I can repair the thread. I'm surprised that nylock nuts aren't used in that location but for some reason they aren't nylocks on this car (same on the lower shock mounting on the other side (which is a different situation - it needs the outer CV replaced and steering boot on that side replaced too). Perhaps the lower shock mount nuts should be nylocks?

Craig.

Reply to
Craig's Saab C900 Site

Seen the photo in the haynes manual. Yup, bigger than a 10mm thread and a 17 or 19 mm nut.

Still it makes no reference to torque settings.

I have also checked a newer manual (thus thiner) that makes no mention of torque settings for the same bit.

Bold = bolt :-(

The Nylock nuts are OK. (perhaps best as one use nuts). SAAB used in those times many different threads (finer threads than the normal metric bolts) and sometimes their nuts used a different (softer) metal instead of plastic to do the locking.

I wonder if new SAABs have a lot more nylock nuts ... cheaper etc.

Sang the photo in the book and anticipating a cross threaded nut ... I would try to put a cut, diagonally, on one of the flats of the nut (the most accessible flat side) with a hacksaw. Anything to weaken it...

Keep at it ... better you than me.

Charles

Reply to
Charles C.

Reply to
Charles C.

John B said he thought about 19mm. Sounds about right from long ago memory (and I'm not going out in the dark and a windstorm to look right now either!) Bentley says 66 - 74lb/ft. Cheers

Reply to
hippo

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