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Body mount subframe rot?

4K views 6 replies 6 participants last post by  Jonesy71 
#1 ·
Hey All,

I have a 71' 2-door and just got a brand new full front suspension polyurethane rebuilt kit from PST with new front shocks. Just tore down my subframe and was stoked to paint/rebuild the front end but I found lots of rot around the body mount areas on the subframe. Also, there seems to be rot in the welds that hold the pieces of the subframe together. The welds have alot of holes in them, looks like swiss cheese. Hello monkey wrench :bored:! Any suggestions on how to fix this? Has anyone welded in the subframe mount reinforcing brackets which i've seen in the YearOne catalog etc? Also, should I consider grinding down all the welds holding the subframe together and rewelding them all? I'd rather not have to get a replacement subframe or travel to have to pick up a used one. I appreciate any feedback or opinions.
 
#2 ·
If your subframe mounts are in bad shape, take the time to do the reinforcing brackets. I have not done this personally, as my mounts were in good shape to begin with.

The welds on the rest of the frame are not pretty. It was this way from the factory - they didn't take a lot of time to weld the frame together. You can fill weld in the areas that have holes, but I would not suggest grinding down the original welds and re-welding. Also, I would not suggest grinding down the welds where you patch the holes - grinding welds actually weakens the weld strength.
 
#4 ·
#5 ·
subframe mounts

I agree. There are plate steel peices you can buy to replace rusted body mount holes, or just go and buy some stock steel and make yourself. Thats what I did. I have pictures if you would like to see them. I , too, had some spotty welding on my subframe, but I just ground down the bad spots and re-welded. I spent some time grinding down crappy welds from the factory...(where was Quality control?)
 
#6 ·
Now theres rust and RUST! LOL I like to use an automatic center punch (spring loaded) and hit every rusted spot a few times till I hit real metal. If its too rusted for that I grab the hammer and solid center punch. I like to see just how deep the rust is. I purposely try to break through if possible. I hit hard till I hit pay dirt. Either metal or air. All the while looking for the underlying metal.

If you find its actually mostly surface rust, and the structural integrity is fine I would wire wheel with a knotted wheel all the way through the orange to shiny metal and weld over.

But if you get into some spots where you can hammer a chisel or center punch through then its time to cut out the cancer and weld in new steel. JR
 
#7 ·
Subframe input

Thanks for the feedback everyone. I like to get a general consensus on things before I make a decision to prevent the inevitable bad decision that happens way to often :bored:. I did consider welding in washers but will wind up getting the kit with the new plates to weld in. I will cut out the rot instead of welding right over to avoid the "shim-effect" paddy71. By the way, thanks for the pics, they look good. 327heaven, do you think you could post those pics you said you have? I will spend alot of time welding in the slop that GM calls welds on the subframe. Thanks for the input everyone, im off to check the YearOne catalog for the plates!
 
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