Thread on welding up the front suspension points to ensure against/repair fatigue cracks....rust failure to the front frame....fine...BUT....

just exactly where and how to spot any potential cracks and damage....OR should I just take the damn thing apart and get my buddy to change his welder over to my house and TIG the damn thing up.....
at what point is this a good idea, and please anyone with knowledge describe what I"m supposed to see....where to look....

GENE

 

Looking foreward to this one.

 

me too, I'm in the middle of taking mine apart for a complete front end rebuild right now. I have no idea what to look for!!!

 

my frame has cracked on the inside rail near the PS pump. It has cracked on the passenger side ahead of the fuel pump. The lower A-arm mount rear bracket has pulled away from the frame twice.

I wouldn't be surprised if another problem rears its head again in the area of the front of the frame.

a few months ago someone was compiling frame issues i don't remember who. Maybe he will chime in.

 

TTT, I had heard the frames varied through production years for gauge of metal, and either the earlier (72 frames) were lighter or heavier, heard both ways...than the later say '78 up sharks....maybe an effort for stronger/heavier in later years....or just the opposite in order to save weight???

GENE

 

I've seen several cars with ugly cracks and weld separations on the front crossmember near where the lower control arm connects and around the shock mount/spring well. There was one fellow posted here a couple of years ago had the lower part of the crossmember rip completely free on one side when he went over a speed bump the wrong way. It seems to me it's more common in the later C3s, but it's pretty common across the C3 model years (and probably C2 as well since it's the same frame, but I don't know). Most recently I saw serious cracking and separation in this area on a '78. All you have to do to spot this is get under the car and look closely at the crossmember--it'll be obvious.

JB


[Modified by JB, 12:01 AM 1/6/2004]

 

there have always been problems with the lower a arm mounts, this is because of torsional warping of the frame. The 80-82 frames have a little beefier supports welded to the frames than the earlier years but still there is room for improvement. Welding it up and fixating the front end is the best solution (spreader bar). Take a close look at the mounts, if you see cracks in the welds or any other cracks in the metal (remove paint/coating) you have a problem. I've also seen where the lower panel of the crossmember comes loose from the rest, there's only a few spot welds along the side.

I had pics of it but can't find them :(


Here's the section you need to check, those 2 channel supports and the weld between the lower panel of the crossmember and the sides of it, the panel extends all the way to the spring pockets

 

Hi Gene , Wondered where you were. Tig is NOT the way to do it. I can easily Tig them myself in the shop but Tig doesn't bit like mig. You want to add metal, tig is too slow.
The U channels the are on the crossmember under the front of the motor where you Lower A arms mount are spot welded to the frame. New they are nice and tight, no gaps between them and the crossmember. As rust builds up between the crossmember and these channels they start pushing the channels away from the crossmember. This opens up a gap where you can start inserting a screwdriver or something. They are slowly walking away from the crossmember.
For something as important as the lower A arm mount it should be as rigid as possible and them GM Corvette manual recommends gusseting this whole area.
While at it look at the flimsy frame where the sway bar mounts. It is just an L make from light sheet metal. They also recommend boxing this area but that runs into other problems so I ran a 3/16 gusset plate from the A arm U chanels into the sway bar mount doubling the thickness of material around the mount.

 

Hey Gene, you beat me to it. I am the one that has been compiling information about the failure modes on the front of our frames. I've also been formulating an analysis but I haven't had the time to finish it. This and Norval's thread may get me in gear to finish it. I have a lot of pictures from other people as well as my own experiences and pictures from welding and minor frame damage on my car. I'll try to get this together soon.

 

Oh, i forgot.

the portion of the frame where the upper spring passes through has cracks right now. This is not where the upper part of the spring sits but the area lower which surrounds the spring (pocket area).

 

OK, some 20 years ago I was immersed cold turkey into an engineering/constrictuio project involving NDT work on jet engines, our machine rode the stress surfaces of intake fan blades and rotor hubs looking for tiney stress cracks in the titanium, so small it would take die pennetrant and a microscope to find....such taking a week or more of time, but our machine did it with RF probes/coils in less than a day....for 250 grand....thank you very much....
at any rate, I am more used to thinking of tiney cracks that I certainly can not spot on something as crude and dirty/greasey as my frame....not that it's a turd ball or anything, but it's not slick titanium either....

So I wonder just how critical I have to be in looking at what I see,.....
and how to make a judgement as to longevity of what I have,,

my buddy only does TIG, no MIG.....unfortunaetly we ain't rich so can't afford a MIG...easy that is....some day may have to buy one soon way things are going ....

but for NOW...no MIG....

I can see the necessity of popping the lower a arms off the frame, but leaving the shock in place, can I have any reasonable hope of bolting them up again?? or do I have to pull the joints loose?? and so can it be done RIGHT with the engine in the car, or is this getting to the sublime allready...
meaning a repeat of the situation 2 years ago when everything was apart, and so have to go there again....

I was under the ASSUMPTION somehow 2 years ago that the frames were fine unless rusted out, or accident damaged, or maybe that was totally optimistic???
you all speak of passing a screwdriver through where the rear lower mounts are coming apart...so I wonder if maybe just WHERE in those tabs ( as I would call them) would that situation apply??? I agree they look flimsey...
but then again I have seen pix of the front two bolted into that little bar/bolt thingy pulling the cross section apart...but I assumed that was rust/accident related...NO????

you all mention some sort of brace in that position?? easy to comprehend, but, well....since there is no apparent rust should I be happy the way it is, or should I pay heed to the wide tires and enthusiastic cornering my wife complains of???

not to mention the ~460 lbs springs in the front.....

GENE