Are 72 and 73 trailing arms the same? the answer..

[tobluforu]

Is yes-oops! But what was sent me was a 71-i was told it was from a 72. After droping the eng. and trans, waiting for used trailing arm to show up, taking old arm out, pressing new bearings into hub, pressing new bushings into arm, installing arm, bolting eng and trans back up, putting everything back together except... now this is the $64,000 question, thats right the.... shock! And guess what?? the shock mount on a 72 and 71 are totally different. The 72 arm shock mount extends toward the back of the car about 2" more than the 71. Plus, the bolt that attaches the the shock to the arm will not fit into the hole on the arm-to small. I tied to hook the schock up and it rubs very nicely against the half shaft. I can't tell you how pissed i am at myself for not checking this out before i went through 3 days of work.
Anyone have a arm (passenger side for a 72?)
Thanks for letting me vent.

[orbmedia]

I thought the change was made in '71 where they modified the inclination of the shock. But didn't know it effects the trailing arm Are you sure your trailing arm is not from a short wheelbase car or something?

[Early_S_Man]

The answer, of course, is ... with the exception of the RS 2.7, YES, per the parts catalog!

You obviously didn't get what was advertised, or they made a mistake in sending the wrong part!!!

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[tobluforu]

Hey s man. My car is a 72. Just what year arm was sent to me? Did i receive a 71 arm. It also had a ball welded on it that the swaybar attached to. Mine didn't. Is it an earlier year or later year based on the shock mount. And, what year(s) will fit on a 72?
thanks

[This message has been edited by tobluforu (edited 11-08-2001).]

[Early_S_Man]

Since it was a steel control-arm, it would have to be an earlier year, because all later-than-73 arms are aluminum. If it came with hub and CV-joint flange that takes 4 ea. 10 mm Allen bolts, then '69 thru '71. All control arms for cars with anti-roll bars prior to '77/'78 had the ball-stud for attachment.

The only direct-fit replacements for your car are '72-'73, but aluminum '74 arms are a fairly easy upgrade. I know an individual PelicanHead in the bay area who is upgrading a '73 'S' to aluminum control arms ... want him to email you?

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[tobluforu]

Thanks s man. Must be from an earlier year. Do you know why porsche changed the way the shock was mounted from 71 to 72?
If i were to change to aluminim arms, i read that i would have to get the hubs as well. Is that all that is needed for the upgrade?
Yes, have your friend email me at lmsolon@hotmail.com.
Thanks for all your help.
Sorry to all for the original post about 72 and 73 arms NOT being the same-oops!

[Early_S_Man]

As far as a reason for the change in '72 ... it was the 'bigger' size and bulk of the 915 transaxle, as your shock rubbing on the half-shaft proves!

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[911pcars]

Porsche changed the geometry of the upper and lower shock mounts around that time. However, this necessitates different shocks as well (as you found out). You'll need units for the later 911s with the larger lower bolt attachment. Depending on the OD of the rear shock, it'll now be a very close to the heat exchanger sheet metal (different exhaust system on 75 and up cars). You may have to delete the shock dust shield and massage the heat exchanger sheet metal to clear. However, it only comes close on full suspension drop.

The later hubs use a larger bearing and the u-joints have a different bolt pattern (6 bolts versus 4). Not sure if the axle shaft will fit into an alloy hub, but the bearing numbers are different starting in '74. I think you'll have to change the outer u-joint to accomodate the late 6-bolt u-joint drive flange (if your arms have them).

Any alloy arm can be used up to '89 (?). The only caveat is the sway bar mount; ball joint up to 77/78, threaded mount thereafter. The camber and toe eccentrics need to be upgraded to alloy compatible units as well.

April '96 issue of Excellence had an article on upgrading to alloy arms that addressed most of the issues.

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

[MMARSH]

TOBLUFORU

I have the steel arms from my 72 if you need one. they are in good shape. I replaced with aluminum ones. Let me know if you are interested.


Michael Marshall

[jluetjen]

I recently updated my '69E to alluminum trailing arms and learned a few things that might be helpful to anyone doing this update to an early 901 tranaxle equipped car.

The trailing arms for '76's will not work with 901 transmissions unless a couple of changes are made. All of them are doable. I've been told that the '74's and '75's will not have all of these issues.

1) As described earlier the shocks and lower bolts will need to be updated to match the trailing arm. Be sure to get bolts with the correct threads, I stripped mine and had to put in helicoils which were a project unto themselves. (Thank-you McMaster-Carr!)

2) The shocks (I used Boge) can be put in with the dustshields, but the heat exchangers need to be modified with a hammer.

3) About 1 inch of the lower shock mount needs to be milled off of the trailing arm. I was able to do mine with some cut-off wheels.

4) My used trailing arms came with the bearings and such installed. But they interfered with my original halfshafts. To make a long story short,I needed to replace the CV Joints, axles and the transmission flanges with '76 spec parts to make it all go together.

5) In order to make the axle flanges from a 915 work in my '901, I had them machine down the diameter of the shaft that goes into the transxle by 1mm. Doing this made everything work.

4a) Be sure to get the correct axle flange stetch-bolts for the 901 transmission. There are two flavors, one type has a teat on the end and the other does not. If you use the wrong type, your differential will not work. I would also do one side at a time to ensure that the spider-gear shaft does not settle out of the spider gears (trust me on this!).

Good Luck.

John
'69 911E

[rboylan]

I have some used arms from my 71. $50 apece plus shipping. Thanks.

Rich

[tobluforu]

Originally posted by rboylan
I have some used arms from my 71. $50 apece plus shipping. Thanks.

Rich

Thanks rich, but as i found out 71 will not fit a 72.