Replacing rear trailing arms

[Jesse]

Is it possible to replace the rear trailing arms on a pre 72 LWB with the gearbox in?

Obviously the front bolts need to be cut off since they’re facing inwards but will new M14 bolt slide past the torsion tube from the outer side? Not keen on any fancy split after market bolts so will drop the drivetrain if necessary.

Perhaps there´s a writeup on this anywhere? Didn't find anything through search..


Regards
Jesse

[911hillclimber]

If your torsion spring tube (that the arms bolt on to) has deep dimples pressed into it then new bolts can be inserted.
There was a discussion on this a few months back as part of a restoration thread I think.
Not all tubes have these dimples, and I think maybe it is the 915 box onwards (so 1972 on) that certainly have them, but I think it is not that clear cut.

Not sure this helps, but worth looking for the dimples.(red arrows in this diagram.)

[Jesse]

Cheers, my torsion tube does have dimples but they aren´t very deep..

Hoping there´s a "road side" solution for this but I'm´ probably going to end up removing the whole drivetrain and start slippin´down the.....

Has anyone had success in this matter with drivetrain in?

Regards

[Gary71]

I have a ‘72 with 915 box, tube dimples (not huge) and there was no way the bolts were coming out with the box in.
Sorry!

[aston]

Not sure if this helps but here is an image of the dimples on my car ..late '73

[Jesse]

Getting the sceews out is doable by cutting them but wondering if its possible to put in new ones from the outside..

Ed Mayo suggested that it might work with a tad shorter screws and a thinner lock nut thats able to grab the screw.

[911hillclimber]

I did mine ok 20 odd years ago.
Nuts next to the 915 box, bolts in from the dimples but they are tight. My bolts and nuts were new genuine Porsche parts.
I think this mod was made specifically to allow the arms to be removed leaving the drive train in place as the 915 is sizably larger than the 901 trans.

My nuts are the 'Aero' type, not the bulky nylocs of today. The aero nuts have a fine cut in the head that bite to the threads, and are noticeably shorter than a normal nyloc.( by a mm or so...) The bolt length is prob correspondingly shorter due to the shorter aero nut, hence access is right for using the dimples to align the bolt.

iirc the access is really difficult when all is in the car and getting those bolts out is a pain.
Oddly, I will be getting those same bolts out in a few weeks time to lube the rear end's bushes. Not looking forward to that.
Nearly as bad as drive shaft gaskets....

[fetuhoe]

On a 1972 car the bolts were fitted with the heads to the transmission side of the bracket fitted to the torsion bar tube and the nuts were fitted on the side with the small dimples.

This means that the transmission has to be dropped for a new bolt to be inserted. The bolt cannot be inserted with the head to the outside of the torsion bar tube bracket due to interference with the main tube.

On the later cars with the large dimple the bolt head fits on the outside of this bracket and the nut is next to the transmission and then you can use a full hex head or a 'T' Type Nyloc.

You really have no choice but to drop the motor/transmission or you can use a WEVO E-Z-Pin which, I agree, look a little scary.

You could plasma cut some holes in the torsion bar tube and weld in some shaped plates if you feel really bold

[Jesse]

Thank you guys!!

I’ll be sliding down the slippery slope then...

[Gary71]

It's only a couple of hours to drop the engine/box...

But whilst you are in there...