Rear Banana/Trailing A-arms

[Jack Olsen]

Whatever you call them, I have the old-style steel ones on the back of my 911, and (since one is bent slightly) I've considered upgrading to the aluminum ones. Now, I know the aluminum ones need to be modified slightly to work with an early 911, but that they're lighter, and the bearings they use are larger.

Are Carrera trailing A-arms the same as the aluminum upgrades? I've found a set that I could buy, but I want to make sure they're the right kind.

------------------
Jack Olsen
1973 911 T (3.6) sunroof coupe

[MMARSH]

Hi Jack,

All the aluminum arms from 74-89 are the same(except turbo) the only differance is the sway bar mount.the 74-77 use the same style you have on your car now. the 78 and on uses a slightly differant arrangment and gives you more options with attaching aftermarket rear swaybars. the later ones seem to be the preferred ones so the ones you have should be fine.

One word of caution though. If you can,get them checked to make sure they are not bent. A friend of mine replaced his steel ones(removed engine and tranny)and installed them only to discover they were slightly bent. He now has to pay to have the engine/tranny removed to replace.

Also several articles say you can get them out without removing the tranny/engine. Has anyone done this? I have been told by two different people who tried it that you cant do it. I've decided to wait till the tranny needs to be done.

[Tlook]

I was bombarded by questions as to if alum.would work on the older non alum. All I could say is yes, but it's nice to know now that the only difference is the sway attachment. The older alum.arms have those round knobs
for the sway link to pop in (real Bi@*$), and
78+ have a bolt.

[dbanazek]

I was only able to change the banana arm bushings on my 72 by dropping the engine, which was a blast. I have been told that if the bolts are put in the right way you can do it without taking the engine out. This was from 2 good wrenches in out local PCA, but they have SCs. I tried to put them in the other way but this doesn't look like it will work either. How can you check to see if an arm is straight?

[orbmedia]

Hey Jack,
The trailing arm upgrade sounds like a good idea. I had a '73 and I R&R'ed my steel arm after I bent it at Bridgehampton Turn 4. The drivetrain remained in the car if that's any help.

By the way, you are definately on the slippery slope to making your car a trailered track-only car. Next you'll strip out the interior, install a cage, fuel cell... I've seen it many times. After that you're "starting from scratch" with a new project to go Club Racing. Enjoy and keep us informed.

[dtw]

Jack,
What mods have to be done to put the aluminum bananas in an early car, out of curiosity? Since I've got my car completely apart and am doing lots of other suspension goodies going in, it'd be a shame not to upgrade. I think I've found a pair, too. But I thought it was pretty much a bolt-up swap. I do have upgraded (SC) brakes to bolt on, poly bearings, adjustable spring plates, weltmeister sway, which should bolt up. How about my stock '72 halfshafts?

-d

------------------
Dave
--------------
http://members.nbci.com/dtwinters/garage/

[JerRed]

I too have a 1973 911T, with the bent rear control arms. I have purchased a set of 1974 911S (Aluminum) arms and am gathering parts to swap them out (bushings, bearings, CV parts, Porsche manuals...) What modification needs to be performed to the arms?

[Early_S_Man]

For the '74-to'73 swap, no changes at all ... the CV-joints and axles are identical!

You would be far ahead, though, to make sure the '74 arms have the round pins for attaching factory-style anti-roll bars!
------------------
Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 12-17-2000).]

[ClayMcguill]

Excellence had a great, detailed article covering this a few years back-I'll go through all my back issues and let ya'll know which issue it was, and all the things to watch out for during the swap-I seem to remember the author had shock absorber/heat exchanger interference, and also had to mill away about an inch of the arm at the threaded boss for the bolt.

------------------
Clay Mcguill www.geocities.com/the912guy

[BRAINIAC]

Clay, that mod. was only necessary for the 71 and earlier as they have different shocks and different shock angles than the 72 and later models. As for the engine and trans removal, it isn't necessary on 73 models because that was the first year they made indentions in the torsion bar tube and faced the bolts with the heads outwards. 72 and earlier require engine/trans removal. Make sure you get the hubs with the bananas because the aluminum ones used wider rear bearings and correspondingly different axle flange hubs. The stub axles are the same.

[JerRed]

I would like someone to verify that I would need new hubs for my steel-to-aluminum arm swap. I have the car put back together, and did not research this part. It appears that BRAINIAC is right, I need new hubs, as there are clearance problems (inability to tighten the axle nuts and brake caliper fit problems).

I realize that it is redundant, but I'd like some confirmation about this before I invest more time wrenching.

My local Porsche dealer says that the hubs carry the same part number from 1973 to 1974. By hub, I am assuming that we are talking about the part that accepts the wheel studs. I am thinking that information is incorrect.

Thanks in advance.

------------------
Cheers,
JerRed
1973 911T, 2.4 CIS

[911pcars]

That would be the April, '96 issue of Excellence (page 69) that described the swap onto early 911s. The article isn't real definitive about brake modifications if the al. arms don't have brakes attached (emergency brake on early 911s might be different). Likewise, there are issues with CV joint matching that need addressing and the photo of the shock modif. has the upper bushings backwards, but it's a pretty good stab at the subject. BTW, each al. arm is about 5.5 lbs lighter than a steel one.

Sherwood Lee
http://members.rennlist.org/911pcars

[john walker's workshop]

if you have another set of bolts, you can use a sawzall to cut the old bolt heads off. (do it after you remove the nuts). then the remaining shaft can be removed. put the new ones in from the outside. they just fit. saves the R+R engine/trans.

[EdRogers]

Hi Jack,
Have you been reding the series in european car regarding the semi-restoration of a '70 S? There is a part where he adds the later aluminum arms, he goes into detail about the shock angle(I don't think it applies to a '73 like yours. But it was a good article. This was about three months ago. I could copy and send the article to you, I could scan and send, but it would take a while. Ed '70 911T w/ 930/10

[BRAINIAC]

Just an update on the hub issue. Yes the part numbers are different from 73 to 74 and later. The 73 and earlier have a 901 prefix and the 74 and later have a 911 prefix. Also, the later ones have a protruding snout with three prongs that sticks out into the wheel center while the earlier hubs are flat. The difference is 5mm between the two to provide for the wider bearings on the later control arms.

------------------
Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[BRAINIAC]

OK, got the part numbers.

The 73 and earlier= 901 331 606 06

74 and later= 911 331 065 33

The 901 number may be wrong. I got it off the back of my old hubs. The numbers were a bit decayed.

------------------
Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[Early_S_Man]

From my parts catalog, all '72-'73 models except RS 2.7 use 901.331.065.09 and the RS 2.7 used 911.331.065.07.

------------------
Warren Hall
1973 911S Targa

[BRAINIAC]

Thanks Warren. Where did you get the parts catalog with the early numbers? All I have seen is the 74-89 book. Gotta get me one of them thingys. Sure would beat taking a wire brush to the back of a rusty wheel hub to get a part number. Wonder why my number was so far off. Mine is a 72 so it should maych your number. Must be a part supercession or something. Hmmm....

------------------
Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[Early_S_Man]

Tyson,


I got it from Stoddard's about 12 years ago. It is a 'not quite perfect' photocopy of the last of the dealer paper parts catalogs before everything went to fiche.

------------------
Warren Hall
1973 911S Targa

[Roland Kunz]

Hello

The RS had boxed steel trailing arms. Also the RS had some additional stiffening in the tube house area. The last RS got the new aluminium travel arms I think around # 1000.

Aluminium travel arms will not bend to much they brake under heavy distorsion ( accident ) Watch for cracks.

I would recomend the later SC or 3,2 L arms ( Well if you buy new ones you only get the last, newest version ).

Plus new adjustable 3,2 L blades ( much cheaper then the non adjustable )

If you like to reuse your old rear stabilizer then Porsche has screw in Ballheads for that purpose.

Also the earlyer travel arms had smaler bushings for M12 in the torsion tube. Since 2,2 it is M15 x1,5

And not to forget the threat for the rear shock is M12x1,5. RS with the Bilstein had M14x1,5. All aluminium arms have M14 x 1,5.

Depending on your shock you can rebush or need a new unit.

Grüsse