Steel to Alloy Control Arm Swap - Questions

[Highfield]

You know I don't embark on things without questions, so here goes.

I have managed to swap my steel arms for a set of 1977 alloy arms with the correct socket ARB mount. Come complete with hubs, e-brake and disc (will not be resued). The will be fully vapour blasted and satin black coated on the brake plate etc. and fitted with new bearings.



Before I take my steel arms to the new owner, he has let me keep both sets so I can swap over whichever parts I may need.

So, do I keep the stub axle from my steel arms and fit to the hub of the alloy arms ?

My steel arms have a stub axle with four bolt holes and two pins. The alloy arms have a stub axle with six bolt holes so my driveshaft would not bolt up.



The stub axle on the steel arms in approx 11cm diameter, whereas the alloy one is 10cm - will the steel arms stub axle fit inside the alloy arms ?







Do I need to machine off the three protrusions on the outside of the alloy hub around the big 32mm nut ?

I really need a definitive answer and help before I let anything go.

As ever, your help is very much appreciated.

Ian

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JWHillRacer wrote on DDK :-

You need -
2 Arms (obvious)
2 Hubs for alloy arms - they are the same ones from 74 to 89, but not easy to get hold of when you want them! (many thanks davidppp!)
Bushes etc - Thanks Nick, they worked a treat!
Longer bolts for connecting to the spring plates
Longer adjusting cams
New solid brake pipes
Possibly new handbrake back-plates, depending how easily the existing ones come off, and how rusty they are!
New Wheel bearings
If it's an original 72 car, the bolts for the suspension arms may well be fitted from the inside, so you will need to take the engine and gearbox out.
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[911st]

I swaped out a set on a 72. On the 915 cars the 74-77 are a straight bolt on. I use did not swap out the brakes, axels, or anything.

I think the early 901 chassis cars require some work around for the shock to clear.

[911st]

To clear up I just bolted the whole system up and did not keep any of my old stuff.

[SteveinTO]

I'd be less inclined to start swapping parts from one banana arm to the other. If your wheel fits on the new hub w/o machining I'd leave it alone. Then the only problem to solve would be an axle with two different styles of CV joints. I don't know if all CV's are splined alike. If not, you'd need custom manufacture axles to accomodate potentially the different splines.

Experience has also taught me when you start mixing and matching parts, the axles may not be the correct length to connect the old gearbox to the new banana arm. My experience (not with a Porsche) is that the suspension will cease to function in either bump or droop, or both, if the axle is too short or too long for the application.

Don't want to be a wet blanket here, but be careful regards the axle install. I guess my question would be, "Does the aluminum arm mimic the steel arm in the arc of the CV flange through the entire range of motion?"

I know someone out there can answer better than I.

[911st]

Existing cv should bolt right up. I think the later SC or Carrera arms had smaller CVs.

In 85 the CV and axel were part of the stub axel.

I think the 74-77 was a direct swap for a 72/3.

I agree, don't swap parts except keep the best rear rotor and brake calipers of the bunch.

[Highfield]

My CV has 4 bolts and 2 pins. The alloy hubs stub axle has holes for 6 bolts. Does it matter if I attach my current 4 bolt and 2 pin driveshaft to the 6 hole alloy hub ?

Ian

[911st]

That sounds familure but I do not recall that. Is there a way to pull the pins and add bolts.

If you have to use the pins. No issue here that I remember. If you ever go to a very high HP motor the 6 bolt will be better and you can just change out the outer CV's I would guess.

[Highfield]

I got the big nut off the alloy arms and have the stub axles out.

No way I can shift the nut on the steel arms, so will take to a local garage.

I can then have a good measure up and post pictures for reference.

Ian

[Highfield]

Here is an update on the story so far, and currently going well :-)

http://www.ddk-online.com/phpBB2/viewtopic.php?t=22111

The above information was great, and I had a PM from JWhillracer (DDK). I rang JW and we talked through how he has 1972 driveshafts fitted to 1977 alloy arms, and they are just fine.

So, following Tim's advice, I popped along to Phantom Vehicles (yes, they do restore old Rolls Royce and Bentley, plus a Lamborghini and a Historic Raly Escort in the making) and it took them an hour to remove the nuts from the axles in the steel arms. They ended up using a torch to heat (oxy ?) and a huge vice, breaker bar and scaffold to restrain the lot from moving. Probably used Loctite and never off in 35 years.......but they are free now.







Once home, I simply swapped the inner stub axles between the steel and alloy arms. They are a close fit, but do not have any play, and the larger CV joint fits on OK as well.









The only problem is the nuts do not screw back on too freely, and I will buy new ones. I believe all the heating and forcing to undo may have affected them ?

Next question - is it a no brainer to fit new wheel bearings at this time ?

If so, how do I remove the old bearings, and is the outer hub with wheel studs easily removed ?

If needs be, Phantom Vehicles have a bearing press.

Ian

[Carrerax]

Any more news on this?

[Highfield]

A little delay as I was away on business and then the team at Phantom Vehicles got struck down with a stomach bug !

I hope to pick up the arms on Monday (with bearings pressed out) and then get them over to Redditch Shotblasting for a vapour clean and degrease etc.

Dreary winter has set in big time, so progress will slow somewhat as I have to work on the car outside, and thus need dry weather.

Ian

[Highfield]

I got the bare control arms and removed parts back, so thought I would close this thread with an updated set of pictures of those parts.

I will continue my Refurbishment thread here ( 73T - Brake & Suspension Refurb - Part 2 - Refurbishment ) with the cleaning and rebuild information.





















Ian