Early 911 Al Trailing Arm Problem

dpegan · 11-07-2003, 02:03 PM

I am upgrading my 1973 911s with late model 911 SC Al. Trailing Arms and ran into a problem in getting the early model Hub to work with the later model Arm.

We replaced the bearings in the Al. Arms and pressed the 73 hub into the new bearing in the Al. trailing arm. After bolting the 73 stub axle and original CV joint together the hub was not in far enough on the Al. Arm to get full thread engagement on the stub axle. In addition the caliper cannot be bolted up to the Arm because it does not line up with the rotor.

We measured the off set differences between the early trailing arm and the SC Al Trailing Arm. It appears that the is a 3/8th " difference in off-set between the two. This makes me think that the SC Hubs have different dimensions than the 73 Hubs. In other words the SC hubs are needed to work with the Al. Trailing Arm configuration.

Anyone have this problem? Any suggestions on the best configuration?

Thanks for your help in advance,

dan

Fritz · 11-07-2003, 03:41 PM

You should probably do a search on here to validate. There was also an article in Excellence about 3 years ago that covered this too with lots of details. Unfortunately I am at work and the file where I copied notes about this is at home.

Others have had the same problem and made it work.

Basically, if you use the aluminum arms off of a 74 or 75, it is a smooth changeover. I searched around and found a pair for my 73. They bolted right in along with my old hubs and calipers. The 74 and 75 also have the balls for the original sway bars.

I know that won't help you now

dpegan · 11-07-2003, 04:12 PM

Thanks, I do have the Excellence Article and have read it over and over. It does not address the hub to trailing arm problem I am having. My buddy has an extra set of SC Al. trailing arms with hubs, so I will try and pull the hubs off this weekend and see if there is a difference in dimensions between the 73 and SC hubs..

Zeke · 11-07-2003, 04:23 PM

Read here: 86 aluminum trailing arms on a 69 - will it work?

dpegan · 11-07-2003, 04:34 PM

Milt,

Thanks, it looks like I am having the same problem that "John '69 911E" had and need to go to the later hubs.

cheers,

dan

911pcars · 11-07-2003, 05:40 PM

"I do have the Excellence Article and have read it over and over. It does not address the hub to trailing arm problem I am having."

If it's the article from '96, yeah I know. I didn't address it because I wasn't aware of it at the time. The alloy arms I used already had the hubs in place so it was a simple matter of using the matching CV joints and axles from a similar year gearbox (upgraded to 915 too. If you mix and match, you need to make sure the CV joints are compatible with the differential stub (901 or 915) on the inside and the control arm bearing stub on the outer end.

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

jluetjen · jluetjen's Garage

Dan;
When I did the later hubs, I also needed to do later style halfshafts and CV's. I don't know if the "early" 915's will mate up to the later style half shafts or not. If not you will most likely be able to get away with just replacing the output flanges. I found mine at my local Porsche dismantler.

dpegan · 11-08-2003, 06:23 PM

Thanks everyone,

I'll let you know how it turns out when I use the SC hubs.

dan
73 911s Targa