Trailing Arm Questions

My post got lost in the shuffle, so here it goes again.

I have an '81 SC. The right rear will not toe straight, and I can hear a rotating type noise coming from the right rear that starts about 20 mph.

I replaced the spring plate bushings with the Neatrix ones, and the trailing arm bushings with Poly-Graphite. I inspected the torsion tubes and they apeared straight, with the bars centered all the way in. NO Luck!

My conclusion: bent trailing arm.

The left side will align straight, but is at the end of its adjustability. So I am looking to replace both arms.

My delima is that I have found several good deals for aluminum arms, but they have the ball/socket type anti-roll bar links and my SC has the bolt-on type.

I don't have the two different arms to compare, so I am seeking advise, and answers. Can the ball/socket arms be modified to accept the bolt-on bars? Are the bosses in the same location on the different arms? Can the "ball stud" be extracted or cut off, and then drilled and taped to accept the bolts? Is there somthing else that I could have overlooked?

I have access to a machine shop, so I don't mind spending the extra time to save the money, and minimize the wife's aggrevation, if it can be done.

Should I buy and modify or keep looking for the correct arms?

Any input is valued, Thanks.

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GT911
GordonTaylor@ev1.net
Spring, Texas

Is there any chance of this sound coming from a bad wheel bearing?
I had a noise similar to what you describe, and the bearings turned out to be shot.

I'm right now assembling it all back together, and hopefully the noise is gone..

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1972 911S Targa
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My project!

I'd look into an aftermarket sway bar, made for the aluminum control arms (with the correct end-links ofcourse).

I went through the same thought process with the control arms on my 944 (later ones are aluminum). The aluminum control arms do reduce flexing, and unsprung weight by a big margin. The harshness over bumps is reduced.

You decide if it's worth it! (keeping the car for long?)
Ahmet

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It's all the driver...

I had an alignment shop check out the rear. The "wrench" scored the tires as they were rotated, and they were turning true on their bearings. After his superficial evaluation, he agreed with me that the arm was probably bent.

I suspect the noise is coming from the CV joint, it is very similar to the one that was posted recently with minor pitting, and may be out of place if the arm is bent.

The right side tire-to-flare clearance is only about .5", while it is about 1.5" on the left side.

I do intend to keep the car for some time to come. I bought the car in '98 for $7600 as a running car, and I think I've already passed the point of no return, ie head stud, top end job, new paint, 4 new tires, then 2 more new rear tires, rotery compressor, new A/C lines, dash board, all new rear end bushings and lowering the car,windshield etc..etc..etc.. I've saved a lot of $ by doing all the work myself, but the wife doesn't see it my way, I know I'm the only one in this boat.

I've been working on putting a 17" X 34" A/C condensor in a carrera tail to improve the A/C performance, it gets warm in Texas in the summer, and condensor size is one of the limiting factors for 911 A/C performance.

I've got some real good offers for arms, but they have the wrong links, where do I go from here???

TIA


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GT911
GordonTaylor@ev1.net
Spring, Texas

Hello

AFIK the aluminium trailing arm will not bend, it will break.

Newer arms have an threat and Porsche supplies an screw in Ball to fit them intoi old cars.

It is possible to cut away the old balls and mill an thread in. I did this once and I´m lucky not have to pay for tools and labour. The ball is hard chrom moly and has an special anchore plate put in while casting.

Next time I will have to let them erode out.


First to check are the bearings and if the gland nut is thight.

Grüsse

Gordon,

Be very careful driving the car, as those aluminum bananas are crack-prone when hitting something with a rear wheel! They typically crack, rather than bend -- the way the steel arms would! There is no significant weight savings with the permanent-mold aluminum part, the reason for going to the aluminum was speed/ease of production ... the steel arms were hand-made by craftsmen in small job-shops, and aren't heavy at all!

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Warren Hall
1973 911S Targa

Early_S_Man, I'm sure you have more experiance with 911 (semi) trailing arms than I do, however:

I've studied the construction of 944 front and rear steel vs. aluminum control arms...

The aluminum arms flex MUCH less, they weight significantly less. (keep in mind these rear semi-trailing arms are quite similar to the 911 units)

Also, I've never had them on scale, but the aluminum 911 semi-trailing arms weigh MUCH less than the steel ones. Significantly less? I think so, but that's objectional.

Also, aluminum arms are more expensive to manufacture (in the 944s case), and the steel arms are pressed by machines!
Ahmet

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It's all the driver...

Before you buy ANYTHING have a good frame shop look at the car and verify the basic geometry. You could be, and probably are, fighting a situation where the car has been hit and poorly repaired, hence, alignment problems galore. If you have 'run out of adjustment' my guess is there are problems greater than trailing arms.
Tom

Several months ago my distributor let go. The upper bushing wore out, and allowed the rotating "star" to strike the hall-effect pick-up, what a mess. The magnet from the pick-up was shattered. At $600 for a new distributor, I was in a bind.

I broke out the old '84 BMW 318i that has been parked for 2 years, and started driving it. Getting 30mpg with today's gas prices has been nice, and it is running very well, so I have been able to park the SC until I solve my rear suspension issues. I drive close to 85 miles a day and I don't want to do any more harm, to me or my car.

As for the distributor, here's a good tidbit: I found a BMW 535 Bosch distributor with all the right "guts" in a yard for $50. It rotated in the opposite direction so I had to move the pin for the vacuum advance from one side to the other, and the bushing went right in.

It now runs better now then it ever has since I've owned it. The timing mark used to fluctuate a little, but now it is right on, with no deviation. Of course this only adds to my frustration of exercising restraint, to not drive the SC out of the neighborhood.

The SC is in very good shape, if I can figure how to post an image on this board I will put it in the "OT: second car" post, I do have one with both the SC and the BMW.

I am a very accomplished "wrench", I don't want to take short cuts that jeopardize quality, but I do have to maneuver within a very tight budget. There are a pair of arms on a auction site that are at $39.99 each right now, aluminum, '75 911S, Ball/Socket link. It is hard for me to imagine getting a better deal then these, but a deal is not a deal if it doesn't work.

So I'm still trying to figure out if they can be modified for the bolt-on link. The suggestion for an after market bar may be the solution. I have looked in many catalogs, and most all of the bars are listed '65-'89. In fact I have not seen any bar listed for '78-'89.

Still trying to decide what to do.

GT911
GordonTaylor@ev1.net
'81 911 SC very very fun
'84 BMW 318i very very economical

Gordon,

Well, it would certainly be easier to put the earlier-style anti-roll bar on your car that it would be to modify the arms, if, for example, both welding and machining is required!

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Warren Hall
1973 911S Targa

Tom

That is very sound advise.

The car is Poly-Pewter, no it's not the name of a smurf, it is the paint on the car. When I was preparing the car for paint I found the driver's fender and the right rear bumper extension had been replaced, they were yellow.

I got the car from a friend who bought it in '89, he said he knew the car had been wrecked before he bought it, but didn't know the details. He said he never had any problems with tire wear.

I've always been very careful operating it, but you can't always avoid all the pot holes, so I've been assuming I probably hit a hole that tweaked the arm.

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GT911
GordonTaylor@ev1.net
Spring, Texas