Rear torsion tube, not good - now what.

[Kroggers]

This is not a nice sight, and really not a nice thing to find after having spent close to two days smacking out the spring plates and torsion bars - including the all so fun "cutting the bars to get it all away from the car - on both sides One good news, the other side of the tube is perfect, and the only damage is what you can see in the picture...




The other side...



So, what do I do now? i am not one to give up, and I will not let the car beat me after all the work and effort I have put into it. As I see it I have the following options, but would really appreciate some advice and guidance on best approach:
1.- Cut out the bad part of the tube and weld in a new section - can this be done?
2.- Cut out half the tube and replace it - big job, not sure I fancy it, and do not have the rig to make sure it all goes back together straight.
3.- Try to cut out the rusty part (just bottom section) and do a patch job - probably not good, as it will not be perfectly shaped, and I will have problems getting the new bushing to sit properly.
4.- Make it a reason to change to coil over on the back. Patch the rust, cover it up and forget about it, and enjoy the feel of nice coil over rear suspension.

Have I missed any good solutions, and what would you recommend I do now??

[khamul02]

only on one side, surely there has to be a "easy" fix to that 2 inches or so of rust.

[Kroggers]

Well, considering the car is predominantly used on the track, I want to have good suspension. If I do fix it and stay with torsion bars, then I want to be able to install the ER PolyBronze Bearings. The easy fix that I have found searching here involves welding in a new smaller diameter pipe to cover and strengthen that section. And then fabricate a new bushing - I can not see this work with the ER bearing. The other option is to go to coil over suspension in the rear - tempting, but it will blow the budget for the rear end rebuild

[Chuck Moreland]

Originally Posted by Kroggers

Well, considering the car is predominantly used on the track, I want to have good suspension. If I do fix it and stay with torsion bars, then I want to be able to install the ER PolyBronze Bearings. The easy fix that I have found searching here involves welding in a new smaller diameter pipe to cover and strengthen that section. And then fabricate a new bushing - I can not see this work with the ER bearing. The other option is to go to coil over suspension in the rear - tempting, but it will blow the budget for the rear end rebuild

You could do this and still use Polybronze, just turn down the polyurethane on a lathe fit the new tube. But this just gets the bushing mounted and does little to restore the chassis strength that is compromised.

Seems you could almost as easily weld in the proper size tube. Just cut away all the cancer.

I'm not sure how many layers of sheet metal are in that box section. You may have to put in the replacement tube in a couple sections to properly weld it.

[ianc]

My sympathies. I read your post a few days ago about your difficulty in getting the bar out on that side. What a sight to be greeted with when the bugger finally let go...

Can't tell you exactly what to do. If you did put a tube in there, it would be very difficult to weld the inner end to the existing tube. The car would definitely be worth more with that properly repaired should you ever decide to sell it...

Sounds like you need to find a very knowledgable metal worker and have him come and take a look at it to see what can be done.

Good luck and sorry for the troubles. It may just be your payback for all those bare-breasted Swedish women wandering around everywhere over there...

ianc

[Rot 911]

Do a search, this issue has come up before and I believe John Walker discussed how to make the repairs. It was not for the faint of heart.

Catastrophic chassis failure! What now?

CRASH, BANG Collaspe

[Kroggers]

Thank you all for the feedback and valuable information.

Chuck - How much do I have to play with on the PolyBronze Bearings? If I do undertake the fix suggested in another thread, and weld in a smaller diameter pipe that will slot into the existing tube, how thick is the polyurethane layer? Although I think this is the approach on the bottom of my list - As with everything else on the car, if i am going to do it, i will do it the best way possible....

Thank you ianc - Does not make for a happy Christmas feeling at the moment. Along with the other rust I have found, I have been tempted to consider the replacement chassis approach, but they do not really exist here in Sweden as they do in the US. We live in a high rust part of the world, so it is not easy to find good condition replacement chassis. And I do not even think there is any companies out here who would have one.... But, I like a challenge, so will push on with what I have :s

I am considering making this a good reason to convert to coil over suspension in the back (same set-up as BB2). I could weld in a strengthening pipe instead of torsion bars, and brace the tube as much as possible, and then install coil over sleeves from Rebel Racing on my Koni struts. this will also facilitate the ability to convert to a G50 should I wan to in the future, as the torsion bars will not longer be there.

If the repair to the tube - to make it still operational for torsion bars is more then moving over to coil over suspension, then I see no reason to make the change - what you say, should I embrace the coil over world??

[Chuck Moreland]

You could take the poly layer down as small as 70mm OD

[Kroggers]

Good to know Chuck. Thank you...

[Dixie]

You've found a lot of rust on that car. Perhaps you need a car/tub from a less rust prone area?

[Kroggers]

Originally Posted by Capt. Carrera

You've found a lot of rust on that car. Perhaps you need a car/tub from a less rust prone area?

Yes, there has been some rust in the usual places, but nothing that can not be fixed As I said above, tubs are not as readily available here as they are in the US, and as Sweden is in a big rust band, the chances are that i would have to pay a lot of money to get a car that has less rust - Then I might as well start over again with a new car, and that is not an option on the list...

I will just keep going, and deal with the rust as I find it....

I know that this rust in the torsion tube can also be fixed, and I will do it. My question was related to what approach I should take? And I have now decided that I will do the job properly, and replace the rusted part of the torsion tube with new metal. But will complete all the other cleaning and striping first, so that I can attack all the rust spots in one go.

My plan of attack is to cut the torsion tube just behind the box section (under the rear seat), and replace the complete section. I know this will require me to gain access from inside the car, but at lease I know it will be 100% good.

Rust attack is now scheduled for February 2008 - that gives me January to get the remainder of the undercoating striped and the rear part of the car all cleaned up...

[billybek]

That's a bummer, Paul. It looks like a lot of work but I am interested to see how you tackle it.
Keep the pics coming...

[Porsche_monkey]

I cleaned mine up with a grinder and inserted a sleeve. I think the sleeve was just a piece of large diameter muffler tube, it fit snugly and I welded around the front edge.

Then I just turn the bushing down slightly to make it fit. It's really not that bad.

[scottbooth]

The rust holes inside the torsion tube on my 78 was further inside the tube than on your car - so I was able to weld in a sleeve that sits *behind* the ER bushing. This won't work for you, but since Chuck says you can turn down the bushing some, you should be able to do what PBH did if you want to keep the torsion bars.

I used 2.5 inch (nominal) schedule 40 structural pipe for the sleeve - much thicker than necessary, but it's what I found, and the OD fits perfectly inside the tube. I ground down the thickness at the edges so it would be easier to weld the sleeve inside the torsion tube.

The hard part is welding the inner edge of the sleeve - the part that's deepest inside the tube. You really have to do it almost blind, so it's easy to make a mess. I used a carbide cutting bur in a die grinder to smooth things out.

I opted to leave the remains of the old tube in place rather than try to cut the rusted portion out and weld a new end onto the old tube. It seems to me that it would be difficult - though of course not impossible - to cut out the end of the tube without having to patch up a lot of metal on the inner and outer longitudinals.

I am still planning to run torsion bars (so far) but I am also going to weld in the rear shock tower reinforcements while I have everything apart and stripped, so it would be easy to switch in the future.

Some pictures - unfortunately not all from the same angle, but you will get the idea.


Before



Hole welded up and smoothed out



Sleeve inserted



Sleeve welded in

Now I just need to do the other side...

The welding inside the tube is pretty ugly, but it should hold. Maybe you can do something similar with a thinner sleeve, then grind down the ER bushing to fit. Or, your idea of going to coil overs does open up some other options for reinforcing the area without having to worry about thickness.

Good luck
Scott

[Kroggers]

Thank you PHB and Scott, that does look OK. I will have to select an approach before I do the work, but part of me would like o do it properly and make sure I retain the required support and strength. As my problem is the part of the tube which is stuck inside the box section only, i will have to consider any effect on chassis strength with what ever option I take. I do not like the idea of leaving rusty metal in there, so will have to cut it out anyway and clean up both sides of the box section anyway... I have Christmas time to decide what to do

[Kroggers]

OK, time for an update. I decided it was probably best and easiest to weld a sleeve inside the tube and turn down the ER bushing, so here are some pictures of the steps...

[Kroggers]

Another job done

And now on to fixing this...

[ianc]

Looks good Pal!

ianc

[Swallowtail]

Originally Posted by Kroggers

OK, time for an update. I decided it was probably best and easiest to weld a sleeve inside the tube and turn down the ER bushing, so here are some pictures of the steps...

Sorry to dig out this old threat but that looks like a neat solution. Do you maybe still have to dimensions of the tube you used?

thanks!