Saab Link Forums banner
1 - 9 of 9 Posts

·
Registered
1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
Joined
·
1,029 Posts
Discussion Starter · #1 ·
Doing balljoints on my 89 900i at preset. Predictably, one of the lower control arm shock mounts now has a stripped stread and a ruined nut and I am trying to find out what the correct thread spec is (it's not a metric thread size - looks more like something close to 3/8" or 1/2" UNF if there is such a thing).

However, just a little while ago I had a different idea. Since I happen to have a metric thread cutting/tapping set around here somewhere, I could cut a new thread onto the shock mount that will fit a normal metric nut. I have a fair number of nuts with integral 'washer shoulders' saved from cars I've pulled apart, and plenty of spare control arm mounting nuts (the ones that bolt the bush housings to the car), so they might be a solution too.

I'm convinced the specified torque for the lower shock mount nuts is way too high as I have had at least four lower control arms get ruined when the shock mount nut doesn't come off properly and ruins the thread on the mount and also in the nut itself.


Craig.c
 

·
Registered
1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
Joined
·
1,029 Posts
Discussion Starter · #2 ·
I found a rural supplies place that is an agent for Case tractors today and they keep a big range of non-metric fasteners in stock. The nut off the good control arm fitted a 7/16" UNF bolt spot-on so I've grabbed a few new nuts of that size to try out. At 30 cents each, I am not complaining!

Craig.
 

·
Registered
1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
Joined
·
1,029 Posts
Discussion Starter · #3 ·
Here is the pic I was looking for the other day showing the stripped thread on another control arm that I replaced on a car I don't own anymore:



flickr page

The arm I am replacing now (I renewed the rubber bushes yesterday using a combination of various sockets in a bench vise to act like a press) doesn't have the thread quite that damaged but it's still not repairable unless I was to try and tap it to a smaller diameter thread size (which would be 3/8" UNF) but that would then be non-standard (for the control arms) and might technically be non-legal.

I haven't been looking at the upper control arm bushes but I know the left side ones particularly are difficult to get at, so I'm leaving them alone for now.

Main thing is that I've got all four of the original ball joints out and replaced with Meyle ones, and fortunately a spare LHS lower control arm just happened to be in my assortment of bits that I brought over from my house in Sydney a while back. :cool:

Craig.
 

·
Registered
Joined
·
3,059 Posts
I had that happen on my SPG. I wound up cutting off the threaded part, then cut the head of an appropriately sized bolt and welded the bolt in place as a new stud.

It worked a treat.
 

·
Registered
1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
Joined
·
1,029 Posts
Discussion Starter · #5 ·
I had that happen on my SPG. I wound up cutting off the threaded part, then cut the head of an appropriately sized bolt and welded the bolt in place as a new stud.

It worked a treat.
That's a good solution. I don't have the resources to do that so I am working with what I have available.

The replacement arm is on the car now (fitted yesterday), and I am still figuring how the torque spec for the lower shock mount nut can be so high since it seems anything beyond about 40 ft-lb causes the thread(s) to start riding into each other and stripping metal away.

So I'm going with 40 (the Bentley specifies a range centred on about 60).

Craig.
 

·
Registered
Joined
·
3,059 Posts
That sounds like it should be more than enough. Most of the load on that stud is pushing down not out against the nut.
 

·
c900 Grognard
Joined
·
3,713 Posts
That happened to me, and the nut was stuck on and would neither fully tighten or come off. I just made sure the shock wasn't going to fall off with some bailing wire, and replaced the a-arm a few months later and used a nut splitter (I had bent the arm on a rock). A-arm replacement is so easy on these cars I'm not sure I'd bother welding on something else, provided you have access to a good junkyard.
 

·
Registered
Joined
·
3,059 Posts
I had to cut the nut off on mine as well. Welding took all of five minutes and was free with what I had lying around the garage.

Unfortunately there aren't the greatest junkyards around where I live in CT.
 

·
Registered
1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
Joined
·
1,029 Posts
Discussion Starter · #9 ·
Refer to the new thread I just started about the after-effects of replacing the balljoints and control arm...

I figured it should be seperate.

Yes replacing the lower control arms is dead-easy. Changing the bushes isn't so easy without the right tools, but I did it with various sockets and a bench vise taking the place of a press. :cool:

Craig.
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top