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Massive amount of frame flex..what do i do?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chaz88K5, Jul 25, 2002.

  1. Chaz88K5

    Chaz88K5 1/2 ton status

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    well last night i finaly had someone around so they could help me...had them turn the wheel back and forth so i could try to find the poping noise when i turn...i got under the truck and watched the frame on the front springs neer the shackle...and the frame was twisting a good inch or more...both rails were doin that...i have a D60 up front wiht crossover steering...could that be whats causing the problem with all the force from that...it almost looks unsafe the way its flexing under there when just sittin on level ground..what do i need to do..or do nothin and let it do its thing /forums/images/icons/crazy.gif /forums/images/icons/crazy.gif
     
  2. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    Flexing L & R, up and down or twisting? Take a look at the crossmembers. Somethin might be loose there, maybe a rivit or somethin. And of course check the steering box, but you already knew that. /forums/images/icons/grin.gif Check the whole frame for cracks to I would think....if it's flexing that much, somethin has to be loose or broken or somethin. /forums/images/icons/grin.gif Good luck fellow Big Dawg. /forums/images/icons/cool.gif
     
  3. m j

    m j 1/2 ton status

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    "near the shackle"
    at the rear of the springs under the cab?
    this is a trouble area on a chev, no crossmembers from the engine back to the rear bodymount crossmember(not sure what blazer guys call that) support the top side of the rails.
    throw in the loosening rivet dilemma and it isnt pretty.
    I think that stitch welding the crossmembers in helps this more then the bolt replacement method.
    my frame has the extra steady bearing crossmember left in to help
    sorry no real solution
     
  4. Chaz88K5

    Chaz88K5 1/2 ton status

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    both frame rails are twisting..and the poping i am thinkin along the same lines about a few rivits loose...i need to check it out more closely next week. /forums/images/icons/crazy.gif
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    ORD Steering brace helps a lot! Check the rivits on the frame> they tend to loosen up. Any that are questionabe or you can spin with a pair of plyers you need to replace with a grade 8 fine thread bolt.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    I know the welding frame issue has been covered already, but how would it work to just weld the rivets in place?

    Obviously if you have a slightly oblong hole already it wouldn't help as much, but as insurance against it happening in the first place, if the metals were similar enough, I'd imagine welding them in place would be good insurance..no?

    The problem I have with bolts is that unless you use bolts with unthreaded shoulders, you have less "load bearing" capacity because of the threads..the frame already is thin, at least the rivets make full contact with it. (ideally)

    Of course, I used bolts through the frame in a couple of places because I had to add things (shock mounts) but even at that time, I figured rivets were actually *better* than the bolts.
     
  7. m j

    m j 1/2 ton status

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    maybe good rivets would be better but the ones chev used come loose.
    the oblong hole thing should be cleaned up when you drill the rivet hole oversized for the larger bolts.
    I think I am missing the load bearing capacity part.
    are you saying the reduced diameter of the bolt shank is smaller then the rivet?
    if so after drilling it oversized I think that part is very close to the same size but I think you are gaining a bunch in material strength using graded bolts rather then soft rivets.
    again I think the stitch welding is the way to go and it made an incredible difference in my old 1/2 ton frame
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    My thinking on the bolts is that unless you thread them in (which I did, but if you did not thread them through the frame) the frame metal, ONLY the threads will be supporting any load, not the full surface like rivets would.

    IMO a bolts clamping force will never be able to equal the load they will see on one of these trucks frames, which is why rivets, if strong enough, are great...they fill the drilled hole exactly, and are kept from sliding back and forth pretty decently. I doubt anyone thinks that the clamping force of the bolt alone is enough, but just wanted to clarify why I was concerned with the thread/surface area issue.
     
  9. m j

    m j 1/2 ton status

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    I may be missing something but I think the bolts out-do the rivets accross the board.
    the nuts maintain clamping force better then the rivet's peened head.
    mine was done with bolts in 1995 and have had no problems of any kind and have never tightened them again
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm not saying bolts can't exceed a rivet in capabilities, only that if the bolt isn't threaded into the frame, and the rivet is a good fit into the drilled hole, (and is of a strong material) the rivet will win in resisting making the hole oblong.

    The threads on a bolt reduce its effectiveness at bearing a side load if they aren't actually threaded into what they are trying to hold.

    A bolt does an extremely good job of holding two things together. But to make an extreme example of where my thinking is, take a rear spring hangar that is normally riveted in place. Remove the rivets, and elongate the holes vertically, so you can "adjust" the height of the spring hanger. I don't believe there is any way a simple nut/bolt arrangement would work to hold the hanger in that case, nor would a rivet. That is just an example of why I don't think clamping force is the end all of holding frame pieces together.

    Sure, clamping force works great for things like the crossmember, where the load is consistently up or down, (weight of engine/tranny/t-case, torquing of the engine would still put up/down load on either end of the crossmember) and bolts work great when trying to keep two pieces from seperating, but I'm trying to think of one application where GM has used bolts that will see a side load, and all I can think of are door hing bolts, and that is nowehere near the load a leaf spring or shock puts on the rivets.

    Obviously GM used weak (or poor fitting, because the rivet would fail if it were weaker than the frame I guess) rivets and or frames, as no one would have oblong rivet holes if they did, but I have a feeling that the rivets are soft as you mention, (or perhaps just assembled poorly? It may all depend on usage...I haven't had a loosened rivet that I detected in 8 years of owning these trucks, but I'm fairly easy on them) and the heads actually loosen up a bit, then allow the load bearing section of the rivet do its work at elongating the hole. Once the rivet loosens up, it works as a lever on the frame, if the load on it is up/down.

    Again, this is a VERY small point, and not knowing it to be absolutely true, I'd say if you used a bolt that was just large enough that it needed to be threaded into the hole, it would be the exact same thing as a properly installed, and *strong* rivet, and there would be no failure problems.

    I like the idea of welding stuff though, tying every bolted/riveted on piece to the frame will only serve to strengthen the frame itself...
     
  11. m j

    m j 1/2 ton status

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    my hangers are bolted in, everything is, doubt the elongated part though, and they have a bracket on the bottom of the frame /forums/images/icons/grin.gif
    sounds like your theory is the rivets resist(or should resist) shear better then bolts.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    sounds like your theory is the rivets resist(or should resist) shear better then bolts.

    [/ QUOTE ]

    Yes. That took a lot less words than mine too. lol. But the key would be if the rivets fit the hole *tighter* than the bolts, only then would that would be true.

    </font><blockquote><font class="small">In reply to:</font><hr />
    my hangers are bolted in, everything is, doubt the elongated part though, and they have a bracket on the bottom of the frame

    [/ QUOTE ]

    Cheater /forums/images/icons/smile.gif

    A bracket on the bottom of the frame obviously would strengthen the entire setup, which is why GM probably did that goofy setup on some of the transmissions with the L shaped crossmember that wrapped around the frame partially.

    The power some of the people on this board put out using stock or fairly stock flat crossmembers, I can't imagine why GM thought they needed that "L" crossmember setup for awhile.

    But anyway, the problem with rivets must be attributed to how hard you work the truck, (or the PO lol) and probably more than anything, how much you force the frame to flex at those rivets.
     
  13. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Rivits were used because they are Cheap and fast and no other reason. While yes you are correct that you want the hole full and a shouldered bolt would be a little bettter I would still bet the clamp force of a fine thread grade 8 will exceed the clamping force the rivit ever though of having. and make it a mute point about the shouldered bolt. My local Ace has grade 8's that starting at 1 inch are shouldered for about the first 3/16-1/4. You have about 5/16's of material and 1/8 inch for a locking washer so 1 inch is a reasonable lenght to use. I beileve the existing holes are about 7/16's bolt size and it's tight fit . 3/8 is loose.
     

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