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

[RichMason]

I have a set of aluminum trailing arms on a junk 86 Carerra in my yard. Will they fit on my 69 E with minimum modification? They are clearly different than mine. What different additional parts will I need? Adjustable spring plates? Different cv axles? different brakes?

Much thanks,

[jluetjen]

Hi Rich;

Based on my swap of '76 aluminum arms onto my '69, I needed to replace the following...

* Trailing arms (duh!). I had to grind some material off of the lower shock mount so that the shocks wouldn't interfere with the chassis.
* CV's (to match the trailing arms. mine interfered on the outside CV's)
* Half shafts (to match the CV's)
* Output flanges on the transaxle (to match the inner CV's. I used 915 axle flanges and had a local machine shop mill 1 mm off of the diameter of the bearing surface. They've worked perfectly.)
* Shocks, to fit the larger bolt of the later trailing arm.

[Early_S_Man]

Rich,

If you use your '69 outer stub axle in the aluminum control arm ... you should be able to reuse your existing 4-bolt CV-joints, since they are interchangeable with the '72 thru early-75 CV's, and certainly strong enough for the job!!!

[West]

They work on my 72', and everything bolted right up, no grinding required - although I don't run a rear sway bar. Kind of a funny story; (before I upgraded the control arms) I was at the track and my car wasn't really handing that well for the first couple of laps. Then, all of a sudden, it got alot better. I was black flagged a couple of laps later and informed that my rear sway bar had fallen off! Well, to make a long story short, I decided that I could live without the rear sway bar. When I put in the alum. trailing arms I went with larger torsion bars and am very happy with the set-up. Go for it!

[jluetjen]

Warren;
I know that there may be some slight differences in the outer stub axles. I was expecting to be able to reuse mine (as reported in the Excellence article), but when I bolted everything together, the bolts that held the stub axle to the CV joint were scraping the trailing arm. I couldn't see it, but I could certainly hear it and feel it. That's why I ended up using the later style stub axle (which fit perfectly) which forced the change in halfshafts, etc...

Keep in mind that Rich wants to use '86 trailing arms.

[304065]

You will also need to modify the later arms to accept a ball stud for mounting the early anti-roll bar, or retrofit a later bar to your car.

I would not characterize this modification as "minumum." More like "Major Surgery." I've been pulling all the parts together to do this over the last couple months, you are allowed to do this modification in PCA stock-class club racing because it does not alter the suspension geometry. Weight savings is about 5 pounds a side, which helps overall vehicle weight and unsprung weight, a good thing for a race car.

But it's a LOT of work for a "driver" and you may experience "project creep" - in my case aluminum arms has become, polished aluminum arms, spring plates became adjustable carrera plates with new cad plating and Elephant Racing bronze bushings, monoballs, new wheel bearings, etc. What starts out as a simple job becomes a $2000 adventure. . . for fractions of a second on the track!

[arrivederci]

Would all of this advice for the '69 be the same for a '72? My '72 is getting the upgrade in the next year and I want to know what I'm in for. At the same time, I'll probably do monoballs, bronze bushings, F&R adjustable sway bars, adjustable spring plates, bigger torsion bars, RS/SC flares, and 7 and 9 x 16" fuchs with sticky rubber. Basically a complete suspension overhaul/upgrade without going to coil overs.

[304065]

Josh,

The '72 has a different diameter shock tube, and the 915 box. The different diameter shock tube will require clearancing of the heat exchangers with a BFH, or removal of the dust cover, to fit properly. Sherwood's article that details relieving the shock mount by a few mm is helpful here. For a '71 I think all I have to do is change the lower shock bushing to accomodate a M14 bolt instead of the M12 that's there now.

Anyway, on the 915 box, you're in luck, the 915s all used 4-bolt axle flanges until mid-75, so score yourself some early banana arms, or if you go the whole nine yards like me, change the six-bolt stub axles on the later arms over to the ones from your steel bananas, and you're in business. If you're doing the bearings, the stub axles have to come out anyway, so there's no greater labor involved.

RS/SC Flares, 7x9's-- are you contemplating a "Prepared" jump from "I" up to "H"? Sounds like I better watch out. . . . you ARE spending all this money so you can race with us at Summit Point this October, right?

[arrivederci]

Right now its just a fun DE car. I'm not entirely familiar with club race classifications and at this point, hadn't really considered it. Time trials is another story...the early 911s, even with mods...seem like they'd be very competitive at the NASA time trials. Hell, I'd probably mop up my class the way the car is right now. All those mods would bump me up one class.

Eventually, I'll do something about the motor. My T motor has dyno'd at ~170 hp, so its already kinda stout. But for competition, I'd like to see around 250 hp out of a high revving 2.7 (if I'm worried about racing classes). If I stick to DEs, I'll go the 3.6 route.