Trunk floor rear crossmember

[73MustangCoupe]

I am working on my trunk floor and tail light panel.  I've got the trunk floor and tail light panel out, and have cleaned up the frame rails, inner wheel house, etc.  I've got the trunk floor set in place to mark the rails, and found that along the rear edge, that the trunk floor is straight, but the crossmember is curved slightly toward the front.  A straightedge along the back flange reveals a 3/8" gap in the center.  

My question is - Is this normal?  I know they make repops for this piece, but it's another $150 I didn't plan on spending.  If you've dealt with this, or know about this, please, I'd love to hear.  Thanks.

 

[IA Rider]

That should be straight. Can it be straightened?

 

[73MustangCoupe]

I was afraid of that.  I will be working on trying to straighten it out tomorrow morning.  I'm not sure what is the best way to straighten it.  I've got some 2 inch square tube that I may be able to use with some clamps to help straighten it.  I'll let you know.  If you have ideas on how to straighten it, I'd be glad to hear them.

 

[73MustangCoupe]

I was able to pull it straight.  I started with some 1 inch, 1/8inch wall square tubing.  I put it along the back just behind the flange that the tail light panel welds to, but when I started clamping it to the flange, it started to bow a little bit.  It did pull the crossmember straighter, but not completely straight.  In the middle of the night, I awoke with the idea to tack a piece of 1 inch angle to that square tube to stiffen it significantly, but not be so thick that my 6 inch clamps wouldn't fit around it.  So today, I got the square tube and 1 inch angle cleaned up, welded together, and once in place was able to clamp the rear flange of the crossmember to it, pulling it straight.  I will have it clamped up to keep it straight while I weld in the trunk floor, and then will be able to remove that tubing, letting the trunk floor keep it in position.  

View from the top, yellow tape is on the top flanges.



Here is the top flange with a straightedge confirming it's straight.



And a view from underneath, showing the clamps pinching the vertical/rear flange, 1 inch square tube and 1 inch angle, pulling the crossmember straight.



So, now that that is sorted, I can get back to work on getting the trunk floor replaced.

 

[IA Rider]

Glad to see you got it straight. Any chance you can put a spacer probably about 3" wide and 3/4" to 1" thick behind eachframe rail ahead of the square  tube then pull past straight starting small at like 1/8" first attempt until you get to stay straight with out the tubing attached? This will make it easier to weld up. When possible I like weld things together in a relaxed state. Be careful if the cross member is rusted or week it might crack. The one on my car was cracked and rusty. Good luck.

 

[73MustangCoupe]

I was thinking of that, too.  I've had it clamped up for a day now, and have the trunk floor ready to go in.  I've got the inside of the frame rails painted with POR15, and tomorrow morning will remove the brace and see how it lays.  I do have some more tubing that I use for a spacer, so I will give that a try in the morning.  Thanks for the tips.