70 Charger Rear Frame Rot

[Philm85]

So I'm currently stuck at a crossroad on what to do concerning my frame rails. On both sides where the frame dips back down behind the axle there is significant rust damage. Looking for recommendations on whether or not to repair each section that is damaged, replace the rear 3/4 of the frame rail, or replace the entire rail? Also, I've already removed the valance which needed replaced and wondered if I'd be better off removing the trunk pan and replacing everything while I'm at it(trunk pan is decent but from the rear the sides appear to be raised up, not sure if it's supposed to be level the whole width or not)?  Any recommendations would be greatly appreciated.

[Charger-Bodie]

Replace the whole rail. Leave trunk floor as a reference until rails are done.

[tsmithae]

Just my  , replace it with new metal.  I did on my '70 and am glad I did so.  Best to get a solid foundation going before moving forward.

[green69rt]

Replace the whole rail. Leave trunk floor as a reference until rails are done.

[68RT440]

I had some pinholes on the rear of my back rails and I ended up replacing both entire rails. I found a nice set of original southern rails so that all of my reference points and fixture that I made fit the replacement rails exactly the same as the originals...

[charger_fan_4ever]

Does not look too bad, appears to be just the bottom flat side. Thats an easy fix for a metal guy.

[green69rt]

One possible problem is that you won't know how bad the rails are till you can look at all the metal, inside and out.   One place that seems to rot is behind the flanges where the leaf spring hanger brackets attach.  And yes, you can patch them sometimes but you really have to be able to look at the whole piece, not just the obvious holes.

[Mike DC]

 
Get under there with an icepick or sharp small phillips head, and start whacking it with a hand sledge, looking for weak spots.  The rust problem is rarely ever as small as it seems. 

[green69rt]

 

 
Get under there with an icepick or sharp small phillips head, and start whacking it with a hand sledge, looking for weak spots.  The rust problem is rarely ever as small as it seems.  

[Philm85]

I'll hop under there and do some work with the screwdriver as mentioned, I'm still expecting on having to replace the whole rail, just want the rear to be solid as possible and definitely don't want to cut any corners. I'll be sure to post what I find when I get all the rot cut out.

[tsmithae]

Just to put it out there... you wouldn't want to do all this work, hit the gas, and have the framerail bend or break.

Just consider that while you mull it over.

[Philm85]

I decided to cut a couple inspection holes towards the front of the frame and the amount of junk and rust that came out helped me decide to go ahead and replace the whole rail on both sides. Now the problem comes to how to exactly tackle this, many guys mentioned use the trunk floor as a reference, only problem I have with that is that the floor has been replaced before and from what I found it was almost 1/2" lower than the factory floor and then when I got into the backseat area I found that the floor has been repaired before as well and that the floor area around the frame rail had cracked. Doesn't make me comfortable to go off of the floors since who knows what has happened to them in the past. So should I replace the back seat area and then go from there or replace the rails and spot weld them in the solid areas before starting with the floors again?

[green69rt]

Just from the pictures you show, it looks like you're getting to the point of building some sort of jig to help keep stuff straight.   Are you confident that the frame, as it sets is correct?  If not, you might want to spend some time measuring the frame to see if it square and level.  Or, you could take it to a frame shop and have them do it..

Once you know the existing frame is correct then build a jig to keep things aligned as you replace parts.

Looks like you'll end up replacing the rear frame rails and the front and rear spring hanger brackets, maybe the rear cross member and the gas tank brace not to mention patching or replacing the trunk floor and rear pass compartment floor.  Just a little warning, be prepared to see the rot in the rockers.  Don't want to discourage you just a heads up.   A jig will make all this replacement much easier.

[Moparsaver]

     No discouragement here either but that is a ton of rot.   I would suspect there is more.