Torsion Tube Molestation

[scootermcrad]

Made an unfortunate discovery this weekend on the '70. My torsion bar tube is pretty much screwed. Having a hard time visualizing what even happened here. I know the car had a 3.2 with a 915 trans in it at some point, so I'm guessing that someone with a big hammer and no brain got in here to make it fit, but maybe someone can enlighten me as to what/why someone would try and modify this. Obviously HOW they did it is ridiculous, but I'm trying to wrap my head around what would have happened here.

Also... what is the CORRECT way of replacing this tube? I'm replacing the floors and rear seat pans in this car and suspect replacing the tube with the seat pans out, will be best, but any insight would be appreciated. I'm thinking I may want to add some additional temporary bracing during this process. I may also need to start thinking about seeing a therapist.

Here's the ugliness (barf)

[scootermcrad]

On a side note, I've been planning on building an I-beam frame table, of sorts, to pick up all the suspension points before replacing pans. If there's any additional considerations here to incorporate into the table for this job, I would like to know.

Thanks guys!

[jpnovak]

The two indentations are factory crimps that help locate and secure the center splines for the torsion bars.

A bigger worry is the fact that the torsion bar appears to be sheared off due to rust at the edges of the trailing arm mounting ears. It needs to be replaced before the car goes back on 4 wheels.

Search for replacement. Usually cut out, align, weld and sleeve is the general method.

[john walker's workshop]

It just ripped out due to rust. I doubt anyone did anything to it. I've cut the tubes out an inch or so inboard of the "frame" rails and spliced in a good one. Helps to have the seat pans out so you can weld it all around.

[scootermcrad]

Oh wow! Okay. Figured it was cut. I shouldn't be surprised with how the rest of the pan looks. Probably makes sense why the rear end is sitting awfully low with no engine it, also. I'll have to take a good look at the outer rear longitudinal supports as well.

I have a couple lines on replacement LWB tubes.

So how about those replacement procedure tips?

Thanks for the response!

[pete3799]

Catastrophic chassis failure! What now?

[chris_seven]

We have found that the best way is to take out the front part of the seat pan and heel board as a complete unit.

You gain easy access to weld in all around the tube and you can easily fit an RS Style Strengthening panel that we have been making for some time now.







When you replace the pans and heel board it looks quite neat.



Tubes are becoming difficult to find and the condition of used parts will be a little variable.

We are looking at making a new section of tube as Porsche can only supply a tube from a Turbo which would need mods to the trailing arm brackets and they are $1500 - ish each.

[Rodsrsr]

Perfect excuse to put a G50 in now.

[scootermcrad]

First, I need to start my response here by saying, I HAD NO IDEA! I had no idea this could happen. Rust is a powerful problem! It explains everything that is going on with this car and I'm only hoping no other damaged occurred when this tube let go. I'm super motivated to fix it. I'm not going to let this car beat me up.

Is there a document somewhere that would outline some key points on the car so before I do this I can check everything out, as far as key suspension points, engine mounts, etc.?

Also, I was planning on switching to aluminum trailing arms eventually. I really wanted to get the car rolling with the steel ones. Is this something I need to consider when looking for a tube? I have a couple leads on good tubes, but I should probably get the right one for the job.

Originally Posted by pete3799

http://forums.pelicanparts.com/porsche-911-technical-forum/286940-catastrophic-chassis-failure-what-now.html

WOW!!!! I just learned a TON reading through that thread!! Holy crap! It also gave me some confidence as well.

Originally Posted by chris_seven

We have found that the best way is to take out the front part of the seat pan and heel board as a complete unit.

You gain easy access to weld in all around the tube and you can easily fit an RS Style Strengthening panel that we have been making for some time now.







When you replace the pans and heel board it looks quite neat.



Tubes are becoming difficult to find and the condition of used parts will be a little variable.

We are looking at making a new section of tube as Porsche can only supply a tube from a Turbo which would need mods to the trailing arm brackets and they are $1500 - ish each.

WOW! Thank you for posting that, Chris! I appreciate it.

I'm confused about the RS panel you speak of. Tell me more about this panel. I'm definitely going to take the "while I'm in there" approach!

Thanks everyone! Learning a ton about this horrifying issue!

[chris_seven]

Should have typed RSR panel.

This is a steel plate that welded to the centre of the torsion bar tube and to the gear shift tunnel.

It is around 2mm thick (0.080") and braces the tube quite well to help prevent the type of failure you have seen.

It was used on factory RSR Race Cars.

While you are that deep into the shell it may be a good idea as they are not expensive and you may never have another chance.

[scootermcrad]

Originally Posted by chris_seven

Should have typed RSR panel.

This is a steel plate that welded to the centre of the torsion bar tube and to the gear shift tunnel.

It is around 2mm thick (0.080") and braces the tube quite well to help prevent the type of failure you have seen.

It was used on factory RSR Race Cars.

While you are that deep into the shell it may be a good idea as they are not expensive and you may never have another chance.

Okay, I figured that was that panel you were referring to. Makes complete sense. Is the RSR bulkhead/heal panel also thicker? Almost seems like a thicker heal panel with that portion welded in place would also be of benefit to help pull it all together.

I'm doing floor pans and seat pans, so I will do this modification at the same time. The car will not be a restoration, so I have no reservations about making any "improvements" where it might stiffen things up.

Thank you Chris!

[Rodsrsr]

Im not kidding about the G50. If you plan on a big motor like a 3.6 or a turbo, the 915 wont be able to handle it for too long and the long bellhousing G50 install requires that part of the tube to be modded anyway.

[scootermcrad]

Originally Posted by Rodsrsr

Im not kidding about the G50. If you plan on a big motor like a 3.6 or a turbo, the 915 wont be able to handle it for too long and the long bellhousing G50 install requires that part of the tube to be modded anyway.

The plan is for a 3.0 or 3.2 with 915 trans. But yeah, good point on the larger motor and G50 conversion. Does it get notched or something?

[scootermcrad]

Okay. Based on everything I'm reading, it appears that I need a pretty specific year-range tube. Most importantly, not a tube from a SWB car. What is the breakdown for what I can use? Sounds like a later one COULD potentially work, but no really solid answer.

I have a line on a '67 tube (an SWB car, obviously) that a friend of mine just cut out and was going to send it to me, but sounds like that might not work. Would the splines be the same or is it just a totally different animal?

Has anyone here used the spline portion, a new tube, and welded on the correct trailing arm mounts?

[scootermcrad]

Oh... and if anyone happens to have a tube that's good and solid that will work for the application, please let me know. THANKS!

[19-911-65]

PM sent, Glenn

[scootermcrad]

I hate to bump up such an old thread, but since the work (after all these years) is still on the back burner until my current other projects are complete, I'm still kind of planning and sorting out some things.

That being said, to post an update, I received a decent looking rear clip section with tube and and torsion bars still intact from Glenn who posted above. THANKS AGAIN, Glenn! Was great to meet you! Should be a good swap, with a little fixturing...

HOWEVER! Lately, I've been thinking a lot about the possibility of running rear coil-overs in this car (maybe even fronts as well), which would eliminate the need to surgically replace the tube, and more or less make repairs structurally, instead. I guess this would also leave me open for a later drive train option as well, although it's not really in the cards right now. I like options though.

Thoughts on just fixturing up the mounting ears and making structural repairs then going the coil-over route instead? I think I heard/read somewhere that the shock towers on earlier cars (1970, in this case) are at a slightly different angle? I'm not afraid to make modifications here, also (with fixturing), if need be to run an off-the-shelf set of rear coil-overs. Thoughts!

Thanks!

[Jack Olsen]

The anchor is heavy, so there's some benefit to tearing it out. We cut into it on my 911 in order to allow the engine and transaxle to be migrated forward (to improve overall weight distribution). But my car also got additional chassis reinforcement (above and beyond the usual coil-over stuff) because of the piece we took out.

[Tremelune]

Just echoing the sentiments of the G50...For the cost of replacing the tube, you're halfway there. G50 cars carry a $10k+ premium over 915 cars. It's free money, way better shifting, better strength for any future motor, the cost being a few grand up front and I think 25 pounds.

I would weld in shock tower supports for coilovers whether you go with them or not. The expensive part is removing the motor, so you might as well give yourself the option in the future for short money...

[Jack Olsen]

Tremelune is correct, but... one data point in the other direction is that I've been running a Magnesium case 915 with a 3.6 for something like 15 years, now -- club racing, time trialing, street driving, and track days in the triple-digits.

But a G50 is stronger and shifts in a more-modern manner.