Question for the e-body body experts...

[Grec]

Background: Car is a '73 Challenger that started life as an auto and was converted, prior to me owning it, to manual. It currently has a 440 Six-Pack with an 18 spline A-833.

Problem: The person or people who converted the tranny apparently used a torch, and not very skillfully, to cut the floorpan to make room for the A-833. When they did this, not only did they leave a jagged whole that was covered with haphazardly riveted sheetmetal, but they also cut into the torsion-bar crossmember that loops over the tranny. It was not cut all the way through, just on one side of the U-shaped crossmember.

There is an approximately 1 inch x 2 inch piece missing from one side (towards the read) of the crossmember where it loops over the tranny. The exact area is where that second smaller tranny crossmember bolts in. In fact, one of the holes for this other brace is missing.

Hope that description makes sense.

Question: Does the entire crossmember need to be replaced? My friend, who is a 20 year professional mechanic, is insisting that the structural integrity has been compromised to the point that replacing the entire torsion-bar crossmenber is needed. Frankly, I question that diagnosis but I wanted to get some other opinions from Cuda / Challenger experts before we went ahead with such MAJOR surgery.

What do you think, guys? Would repair of this with, say, some cleaning of the edges and welding in of steel do it, or is replacement the only way to go? Does this crossmember, at that particular area, receive enough torsional flex to warrant replacement?

[rallye73]

My car had the same thing happen to it. I had a spare cross member to install, but it made more since to just section in the part that was butchered. It was easy since we had the tranny tunnel cut out for the four speed hump. That let us weld in the repair section on both sides prior to putting the hump in. Just be sure and tack weld some braces in before you do any cutting.

[Grec]

So you cut totally through the crossmember, removed a section and replaced with a donor piece?

[E-Body Products]

I am not an expert... however....

I would recommend not cutting all of the way through the torsion bar crossmember.  Just cut and patch in the missing areas and grind the welds down smooth.   

I also have replacement crossmembers on my site if you choose to go that way.  You can see the pricing on my website if interested.



Daniel
www.ebodyproducts.com
dj1965@ebodyproducts.com

[hemiken]

I suggest that you take some pictures to better help us to help you with a resolution buddy.  But going by what you said in your initial posting, it sounds like a no brainer to me as i would just repair the area in question by welding what is needed and filling what is missing with steel.  But pictures would be much better to make a diagnosise with

[426HEMI]

  with Kenny that it makes it much easier to help when you provide a picture of the problem, 

[A R T]

Question: Does the entire crossmember need to be replaced? My friend, who is a 20 year professional mechanic, is insisting that the structural integrity has been compromised to the point that replacing the entire torsion-bar crossmenber is needed. Frankly, I question that diagnosis but I wanted to get some other opinions from Cuda / Challenger experts before we went ahead with such MAJOR surgery.

NO, it does not need to be replaced. Inside the tunnel is not a structural loaded area. Trim it up neatly, fabricate a section, weld it in place and forget about it. Spend your time and money on other priorities.

 

[femtnmax]

Inside the tunnel is not a structural loaded area.

Not entirely true.  The tunnel floor skin is probably lightly loaded, but the twisting of each torsion bar is taken up entirely by the torsion bar crossmember along with help from the floor skin.   Note that the crossmember is made of a thicker gage metal than the floor skin...so the crossmember is taking in a large load, but it still needs the floor skin to work properly per the original design.
The floor skin surves to cap off or "Box" the "U" shaped crossmember so it can resist buckling.  The two work together to distribute the twisting load of the torsion bars and spread this load out and into the unibody.
If you make a saw cut clear thru the crossmember, then raise one front tire about a foot off the floor, leaving the other 3 tires on the ground,  I'll bet you'd see the saw cut in the crossmember open up.
Imagine if there was no crossmember at all, just a short piece of angle iron long enough to weld the torsion bar recepticle.   The twisting of the torsion bar would twist the angle iron, which would buckle the floor skin around the pieces of angle iron;  that is why mopar made the crossmember span the entire floor skin between the unibody box sections under each door.
Assume the car weighs 3200 lb, with each tire load 1/4 of that which is 800 lb;  and assume the lower control arm of the front suspension is 2 foot long.  The twisting moment is equal to 800 times 2 = 1600 ft lb.   Thats 10 times the best you could twist a 160 ft lb torque wrench.   That torsion bar crossmember/ floor skin combo is absorbing a real twisiting moment load, and it has to do it without cracking for years and years over many thousands of miles.
Welding could work, like said, photos would help make the determination,  but a purist would probably replace the crossmember.
If you do weld, remember to etch prime and paint those welds real good.  The weld metal will rust much quicker than surrounding metal that was not heated.   I have seen unibody welds painted with spray cans that you could put your finger thru 5 years after the repairs were made.

[A R T]

Welding could work, like said, photos would help make the determination,  but a purist would probably replace the crossmember.

And thats what I was implying. I fully understand your thinking, but lets be clear, its a small spot on the top of the tunnel. Its 1" x 2" thats been hacked away in a previous conversion. Sure if its a Hemi Convertible it would be senseless NOT to replace the crossmember, but its a 73 Challenger that has been down the road with this section missing for a long time I suspect, with no problems.
My advice was its not a critical section, go ahead and weld it up and drive it. Nothing to worry about there as far as compromising the structural integrity of the component.
Its all good !!