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Discussion Starter · #1 ·
As I tear the RC down I am finding more items that need attention of note as I was prepping the frame for paint I found these.  The passenger side rear spring front bracket was trying very hard to separate itself from the frame.

I have never seen a truck or RC give problems in this area of the frame, the passenger side has cracks three of the holes that hold the bracket to the frame and the drivers side has one. 

Anyone seen this before? the Gold sharpie is where the cracks are.
 

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Cant speak for the others but I've never seen cracks like that on a ram/rc.  Guessing it was abused /articulated well beyond normal. 

i guess if it was mine, I'd drillstop, v notch the crack and weld it up and grind flush only where I need to keep it flush.  Then weld reinforcements on the backside of the frame (like  jungle  has for the front) and turn it from a c channel frame into a square tube frame in those spots.  I suppose a fishplate could be done on the back side of the frame too. 

I welded the frame on my 93 in 2012 and its still holding up.  220 v or bigger welder though
 

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I also have never seen, or heard of cracks like those, But I also can imagine a truck going its whole life with small cracks like that, that go un-noticed. I cannot imagine the forces that would cause those. I would go with the drilling , welding, and a backer plate
 

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Discussion Starter · #4 ·
That's why I asked, this is a 1990 frame but have never seen a RC/truck give problems in this area from any year.  I am guessing just age and brittle metal and weight and non stop use, as you said the cracks could of been there a long time its odd that the passenger side was way worse than the drivers side.

For fixing the frame I am deffently plating the back side, stop drilling the cracks, grinding and welding where possible.  Boxing the whole frame is also a thought which I was considering anyway. the front has already been done

There is a cross member in this area so it was already a stressed area of the frame, and Doge also dimpled the frame in this same area so they knew it was going to be a high stress area.

My only concern is once I repair/strengthen the frame a lot more load will be added to the spring bracket.  And Im guessing it wont be long before that starts giving issues.  Could make a beefy unit and that should solve future issues.       
 

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I would NOT bother , as said we have seen many and never saw that problem on any of them . I really think the truck was driven over such lumps and bumps it was being twisted way too often and too far as well . 1 other thing that may have had a effect , or been effected , the body adds alot of rigidity to the "whole" was / is the mounts shot/ loose ? I'd drill / weld ream for TIGHT fitting bolts and forget it . a good hardware store or a Caterpillar dealer some grade 8 hardware ( inc washers grade 8 ) really tight fitting bolt shanks only in the holes , and tighten em up.
I have a 1993 w250 who's d/s front frame horn upper flange cracked right in front of steering box , in the dimpled area ( NOT FOUND on earlier models ) ( possible crumple zone design ) I welded it years ago , replaced the cracked box adapter , and its been fine for lots of use / loads / years , its not a city truck either .... it lives in the dirt  ;)
 

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Discussion Starter · #6 ·
All the body mounts were/are good so no issue there.  Ill do something just don't want to go back and have to do another repair after the body is back on it much easier to do all this work now with the truck all apart.
 

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I take it you looked at the other holes for similar cracks. Even thinking of the worst off road situations, I cannot picture how the front rear axle spring hangers would take the shock, but the rest of the spring hangers do not.  All I can think of right off, are steering box,  snow plow, or rust related.
 

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Discussion Starter · #8 ·
I looked real close at everything on the frame bolted and rivited, this RC never had a plow, was in California all of its life so never seen salt.

Im at a loss also of what caused it in this area I agree the force was very high to cause the frame to crack.  The rivets were still tight and not loose. Cross member rivets were also tight in the same area.
 

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yep the rivets did their job , picture the spring perchs attached to a flat plate , now drop one side , lift the other , the springs attempt to follow the canted axle , the 90' at the eye bolt trys to angle to match the axle , that flex's the flat plate , over and over , and it "work hardens" and cracks . "stress cracks "  the important thing for you is  tight fitting bolt shanks in the holes where the rivets were ( NO MOVEMENT ) then squash them tight with good hardware . me ,for normal use ,  I'd use just a flat "fish" plate covering the bolts , drill stop vee groove and weld up the cracks , call it good . you can reinforce the hell outta 1 area , and cause stress in the next , where do you "stop"becomes the question , and how do you spread the load at the area you stopped ....frame flex is going to attempt to happen , you either stop it completely ( easiest way , a full cage ) or spread it out evenly ... 
 

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Discussion Starter · #10 ·
I agree with all of that but this truck was NOT a rock crawler and I know many people that have abused their trucks/RC more than this on ever saw.  But it in now almost 30yr old so metal fatigue is coming into play.

Anyway good discussion, its broke it will get fixed I will keep this thread updated as I make the repair.
 

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Wilsonphil said:
But it in now almost 30yr old so metal fatigue is coming into play.
The metal would have to flex, even a tiny bit. I could see bump stops, the junctions with the cross members, The steering mount, and a few other spots. But a spring hanger? Any road bumps will be dampened by the springs and shocks. I could see the rear spring hanger, if the suspension is cycled enough to bind the shackle. Any forces making its way to the front hanger, I think would mangle the spring bushing. If I remember when I go down to the shop, I'll look and see if the frame specs changed.
 

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yes , after so many years metallurgy ( SP?) comes into play . we know somewhere along the way dodge changed the sheetmetal used on our doors , the 90 plus ones crack all to hell , earlier ones don't  , what if an out of balance tire was always there ? a bad shock ?
 

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Any forces from the rear axle, will be spread between the front hangers, the rear hangers, and the shocks. After being cushioned by the tires, the springs, and the spring bushings.  Does not make sense to only affect two of the six mounting points, or eight of the eighteen bolt holes.

Besides a manufacturing defect/ issue, the only other force I can envision, would be someone pulling on something like tree stumps, with a chain wrapped around the rear axle.
 

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Discussion Starter · #14 ·
I have owned this RC since 2012, IMO I have not abused it, used it yes, abused it no.  Its not an area that I normally pay attention to and I doubt it I would of ever seen it if the body was not off.  Its just really odd as the bushing was good and the bracket looks normal also just the frame is cracked.

No tire issues, suspension issues, good springs and suspension geometry is good.

Springs going flat under compression as you said the rear hanger one would of given problems or so I would think also.  Its is something I can look at but why was one side so much worse that the other.  still a lot of stress to cause that.

It would be interesting to see if the frame specs changed.
 

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Discussion Starter · #15 ·
And I don't do stump removal using the rear axle as a attach point, so we can eliminate that possibility.
 

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I did not intend to imply you did. That type of force, is the only type that I can think of that would pull on the front hanger, and not effect the shock mounts, or rear hanger.

I looked up the 79, 85, and 90 frame specs. They are all identical. They could still have changed something like the steel alloy, that is not listed in the book. Would be interesting to know if the holes were punched, or drilled.

Quite likely something that effects many RC's, just never noticed.
 

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frame specs , I do have a few fsm's they have the size/load capacitys for the various models , this IS a '90 R/C? I have a '90 book , what I know from my years as a heavy equipment / truck mechanic  about those cracks is this , the spring perches are not flat , the bends you see give it structural rigidity , which keeps IT from flexing . Repetitive flexing is what caused those cracks , a flat hunk of steel will flex much easier than one with a " shape " , like floor pans , the little ridges give it much more rigidity . My 1 ton , apart here in the "shop" has indents , near where your has cracked ,BUT they are only behind the eye , not in front ,  those are doing something to that "flat" area  .
a '90 was already 22 years old before you got it in 2012 ...  some large trucks ( tandems) would bounce the front/rear duals at highway speeds in a rhythmic motion even with springs / rubber tires/etc that action would eventually tear up ( break)the frame and crossmembers in that area  I have never seen it on a light duty like a p/u but it does happen ...  its from movement of that section of frame , I'd say a twisting motion , it can be an imperceptible amount  , but its movement , no doubt about it .  is one hole of the perch at the spring eye bolt worn , loading one side of the hanger trying to twist it ? or that bolt so short its riding on the threaded portion ?
 

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Wilsonphil said:
I have owned this RC since 2012, IMO I have not abused it, used it yes, abused it no. Its not an area that I normally pay attention to and I doubt it I would of ever seen it if the body was not off. Its just really odd as the bushing was good and the bracket looks normal also just the frame is cracked.
Cracks like these do not have to be the result of "abuse", they can just happen. Not all cracks appear or spread rapidly (unlike the typical GM square body/rock crawler/steering box failure). These cracks could have been in progress for years, without you ever noticing. These particular cracks appear to me as metal fatigue cracks and they usually begin at a stress riser. Probably from a sharp edge where the hole was formed for the rivets. Add in some type of cyclic motion, such as years of suspension or spring cycling, load on the components (Note I didn't say over loading), any natural twisting or frame flex or even weak or loose rivets, and a crack can form and spread. Fortunately it is repairable, but I would add to the repair that you lightly radius the rivet holes a bit to remove any sharp edges. Maybe consider drilling larger rivet holes (Larger holes tend to reduce stress concentrations) and of course using larger grade 8 bolts.

Ed
 

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Discussion Starter · #19 ·
So it looks like all the holes are punched, don't know if the holes are done before or after the frame channels are bent. 

I drilled all the rivets for the cross member that were local to the area I am repairing, as you can see from the picture there was not a lot of effort when assembled to make sure there were good holes notice the gap full of rust and how the rivet walked during install or very poor hole alignment.  90% of the rivets I drilled out looked this way but none of them were loose.

Of note the drop legs of the cross member that rivet to the lower lip of the frame had 4ea holes but only 2ea were used.  Not sure what the tool dimple is from I'm assuming some kind of clamp 
 

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the dirt/rust between the 2 parts show little/no signs of movement . This is the benefit of rivets , it swells in the hole griping each part . Its why your replacement bolt "shoulders" must fit tightly in the hole , the bolts don't swell and only the compression of the nut/bolt stops movement . when large trucks have whats called a "double" frame , the 2 frames made to fit so tightly together you can't put a paper between them , after a few years rust will build up between them , so much so one will split/crack ( outter one usually) .... it IS possible the 2 parts were not clamped tightly together when the rivet was "set" allowing the rail to flex more than it should have , it only has to be in  .001's , just often .
 
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