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Crushed frame rail repair options

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  • #16
    I have the same frame rail problem seems to be quite common with the z31's i have picked up


    • #17
      If you were to cut the frame off and start from new (like what Gary did) how can you stop the body from flexing on you? Is leaving the jack stands under the front and rear suspension adequate enough to stop the body from flexing.

      I have the same problem and was thinking of doing this. 1st drill holes in the frame and fill it with foam via a caulking gun and then weld new metal over the the old frame and make it twice as strong. This way, you won't have rust issues in the future and you'll have a super strong, structurally sound, frame.
      1988 SS #71

      Better to remain silent and be thought a fool, than to speak and remove all doubt.


      • #18
        Did anyone get a result for this problem ... ? It seems every z I've seen has damaged jack points ...


        • #19
          Wow.. resurrecting a 10yr old thread at apparently the right time.

          I've recently created templates that i am currently welding into Shiro 683.
          These are not the entire frame rail, but about the front 2/3 which in my experience is the area that sees the worst crushing.

          I've started on the passenger side as that was the worst.

          Originally i was going to take a piece of 16ga steel and bend it into a 3" channel then cut/weld/shape it to fit the dogleg profile of the
          framerail section. That turned out to be a bad idea and would have involved too much work. The replacement would need to be made out of sections that are welded together.


          I tried a couple different methods of making a template from the section i removed but it was pretty damaged even after beating it back into shape (it was also cracked in 2 places)

          These were pretty close, but not enough.

          I then bought some foam core sign board from the dollar store and with hotglue, created templates from the virgin framerails on my 84T.
          ( ever tried crafting beneath a car parked in the street during a rainstorm with the real danger of the extension cord getting in the times)

          84 AE/Shiro #683/Shiro #820/84 Turbo


          • #20
            I then used post-it notes to then make a negative template of the inside of the foamcore rails and then transferred those shapes to posterboard.


            The posterboard templates were then transfered to some 16ga steel from the local ACE hardware

            Those were then cut out with a jigsaw.



            Video here:


            They are far from exact but close enough for an angle grinder. The dogleg profile of the bottom doesn't exactly match the profile of the edges that get plug welded to the floorpan.
            Using an angle grinder they can be fitted better though. The passenger side rail also needs a section removed and rewelded as a recessed pocket for the speedometer cable
            and with the exception of a scalloped profile on the top, is a nearly mirror image of the drivers side.

            Right now the passenger side is tack welded together with the exception of the outer rail.

            I think for welding, i'd like to run a bead the entire length on the insides then grind the outer edge to a round profile then weld that and grind it back.
            A lot of work, but hopefully it will give the edges a more stock looking less-box-like rounded edge profile and add strength. Also thinking of inner ribs
            at jack points.

            I went back on the wayback machine and found Gary's archived images from his site and found that his method was almost exactly what i ended up doing.

            Still got work to do though, and 2 more cars to do it on.

            Also, i'll rework the templates with the changes i made with the angle grinder and find a way to scan them and make them printable for anyone.

            84 AE/Shiro #683/Shiro #820/84 Turbo


            • dbruce
              dbruce commented
              Editing a comment
              wow ... amazing ..

            • mwolvinm
              mwolvinm commented
              Editing a comment
              Very interesting. I've noticed the doors on my parts car don't open/close cleanly when the entire car is up on jackstands. That's telling me the body is twisting with the crushed frame rails still in vehicle. I'm curious how to keep the car straight when welding the replacements in. These look great btw.

          • #21
            I'm curious how to keep the car straight when welding the replacements in.
            I kept the car flat on it's suspension on a flat garage floor when i cut out the section and now, it's getting welded back in while the car is still sitting on it's suspension on a 4 post lift.
            I do have the front upper radiator support removed but everything else is still bolted in place. I've not removed the bumpers or crossmembers or doors.

            I would suppose you could rig up a scaffold that ties the strut towers in a boxed X pattern (dash and windshield removed) and have turnbuckles at the corners for keeping the chassis stiff and aligned according to the body manual. I've seen some youtube guys do this on restorations. Depends on how much you gotta cut out and repair i guess.

            I think in my case, since i'm not flexing the body and the rest of the car is intact that i should be within tolerance when it gets welded back in. In addition to the drivers side framerail I also need to replace the lower rad support and when i do that i'll replace the bumper with a section of tube steel bolted to the bumper shock mounting points to keep the front framerails in alignment.

            84 AE/Shiro #683/Shiro #820/84 Turbo


            • #22
              Great work! Please do scan them when you get a chance.


              • #23
                This video on crushed pinch weld repair is pretty good ... An interesting tool was fabricated to do the repairs ..

                Crushed Pinch Welds On Your Classic Car? Simple Fix!

                It's not clear how my jack point area got so messed up, but it was ugly. Crushed pinch welds are common on Porsche's because the jack area is only sheet metal. Many classic cars are this way and if the car is lifted incorrectly or unevenly, damage can occur and its expensive to undo. Don't let the tire shop fix it! Ha ha,

                This cobbled together tool removed almost all the damage without screwing up the door gaps or anything else for that matter. It's a simple puller that acts locally on the pinch weld. It does require temporarily welding the puller to the pinch weld. There's a great clip in the video below that shows just how much the flange moves when sped up and reversed a bit. If anyone has this problem and would like to borrow the tool, just let me know. I'm happy to loan it out.
                Last edited by dbruce; 08-16-2020, 09:08 AM.


                • waynedwops42
                  waynedwops42 commented
                  Editing a comment
                  Great find; my jack points are all bent and splayed, I may have use for that tool in the future. I'll need to get a welder and learn how to weld in the mean time...

              • #24
                Wow very interesting, I'm pretty sure all z31 owners have this 1987t has some but not as bad.