Cracked torsion bar tube.

RallyJon · 05-11-2004, 12:17 PM

Well, this is a bummer. My mechanic just called and while he was cleaning things up inside the engine compartment, he found a major crack in one of the rear torsion bar tubes. I did a search and couldn't find anything--does this happen often?

Anyway he found a salvage yard with a donor (a later, galvanized car) and is going to weld it in.

Anyone had this happen? Bad news, but glad he caught it now before the new engine went in.

chrisp · 05-11-2004, 01:20 PM

Can you even see the torsion bar tubes from inside the engine compartment? I thought they were only visible from underneath.

Does it show signs of impact or is it corrosion damage? By the description (a crack) it sounds like a fatigue or accident thing.

Bill Verburg · Bill Verburg's Garage

I've heard of it but never seen it. Usually rust is the demon.

Tspringer · 05-11-2004, 02:06 PM

There is only 1 torsion bar tube in the rear. It runs horizontally across the car, far below and in front of the engine bay. It is in front of the transmission. Replacing this tube is a BIG deal. The car would need to be placed on a proper jig to ensure correct location of the tube, otherwise your suspension geometry could be totally out of whack.

Also.... if it was just cracked, why not weld in a patch panel?

This sounds fishy to me. The torsion bar tube is not something you just cut out of a donor car in 15 minutes and weld up into your car in a couple of hours. Its a major structural component in the car.....

Terry

RallyJon · 05-11-2004, 06:18 PM

Thanks for the comments. I'll get a better idea when I take a look tomorrow and I'll put up some pics.

And my car is a mobile alter to that demon--thought it was exorcised, but maybe not.

Rot 911 · 05-11-2004, 06:33 PM

I agree with Terry. In addition, I have seen rusted out tubes, but never a cracked one. If it is cracked without rust, should be able to weld it.

RallyJon · 05-12-2004, 03:35 PM

Took some pics. Rusted out is definitely a better description than cracked.

RoninLB · 05-12-2004, 03:41 PM

WTF.. dam that sucks.
maybe a good example of water getting trapped under the black coating

Tspringer · 05-12-2004, 04:28 PM

Replacing that thing is a HUGE deal. The rust damage does not seem massive and may be localized. If the torsion bars are out, take some time to really clean the tube out.

Get a small wire brush and use some duct tape to attach it to a steel rod. Then stick it into the tube and scrape like crazy. Is a shop vac with extension to help get all the rust scale and crap out of the tube. MAke sure you wire brush the inner splines as well. Spend a good bit of time on this and really get all the rusty scale off the inside of the tube..

Now get some good scrapers, a propane torch and some grinding tools and have at the outside of the tube all around the obvious rust areas. Get down to shiny metal. Enlarge the holes as much as you can without doing any real cutting.

You have to find out how far the cancer really extends. If when your done the rust holes are only quarter of dollar sized, you can weld in patch panels. You can do a good bit of repair on that section of the tube from below and under the car if you have it on a lift. Its far simpler to repair the existing tube than to weld in a new one!

I would not have a tube welded in without having the entire car on a factory jig. You could easily end up with a shiny new looking car with suspension geometry so far out of whack its not drivable.

Terry

Glasgow 911SC · Glasgow 911SC's Garage

eurgh. I hate pics like that. Good luck.

jess p · 05-12-2004, 06:48 PM

I replaced a torsion tube from a 74 into a 66 912 to make
it a long wheel base car. It is a HUGH JOB!!!!!!!!!!!
I would sand away the paint to see the rust damage and
try to patch it.

RallyJon · 05-13-2004, 05:33 AM

Bert's plan is to retain the ends, which are solid, and replace the center section. You can see one score mark where he's going to cut it out. The ends will locate the position of the replacement. He's going to have to cut an access hole in the seat area to get to the back of the tube.

thrown_hammer · 05-13-2004, 05:42 AM

I suddenly have this uncontrollable urge to drive home and look at my rear torsion bar tube...

Dude that sucks!

chrisp · 05-13-2004, 05:43 AM

Not sure how this piece attaches to the chassis in the middle but if you can cut out the entire middle as one unit and get a replacement center piece than suspension mounting points should be easier to line up because they will already be in proper orientation to each other it's just the alignment of the tube overall that's important.

RallyJon · 05-13-2004, 05:52 AM

Yeah, Chris, that the plan. He's going to make a jig to locate the replacement using the transmission mount brackets.

RPMClassic · 05-13-2004, 06:00 AM

Jon -

Sorry to hear the bad news...good thing your wrench found now vs later. Is this car a stocker or an outlaw/de car? Talk to JackO and have him send you some pictures, but maybe the rear camber boxes from Smart Racing will be a cheaper alternative compared to replacing a stock rear tube. That way you remove the rot and section in the boxes. It requires some mods to back seat area...check out the pictures. Good luck.

Grady Clay · 05-13-2004, 06:23 AM

Jon,

In your first image it appears the torsion bar tube has been partially replaced once before. Is that a weld around the circumference to the left side of the image? If so, you should consider replacing the entire tube with a new spare part and reinforcing the side frame parts. The new part comes with reinforcements that weld to the end of the tunnel and transfer the suspension load to the pan and tunnel. Big improvement.

I agree, have someone do it properly on a jig.

Be prepared to fix other things as you find them. “ An ounce of prevention is worth ….”

BTW, check your rubber throttle coupling. It looks like the rubber has failed.

Best,
Grady

RallyJon · 05-13-2004, 06:26 AM

No--couldn't care less about staying stock--the car's a frankenstein as it is.

Since I already have the threaded Leda rear shocks I thought about ditching the torsion bars altogether. I looked at the pics from BB2, and it appeared to me that you still need the tube (except the very middle) to locate the banana arms and transmission mounts. Plus there's all that reinforcement needed on the shock towers and crossmember there.

Grady Clay · 05-13-2004, 07:56 AM

Jon,

Here are some things to think about:
"

"
(C) 1971 Dr.- Ing. h.c.F. Porsche K.-G.

(C) 2004 Grady Clay

The new torsion bar comes with these two reinforcements that tie the tube, in line with the suspension mount loads, into the tunnel-floor pan structure. It also releaves the side frame of some tortional loads.

Best,
Grady

RallyJon · 05-13-2004, 08:40 AM

Thank you, Grady! Great idea welding on those reinforcements.