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Owners of K-trucks with cracked engine mounts/crossmembers(and BBC owners)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dyeager535, Aug 29, 2003.

  1. dyeager535

    dyeager535 1 ton status Premium Member

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    The typical location for the crack seems to be the passenger side of the front crossmember, on the "back edge", near where the motor mount "stub" bolts in.

    My question for anyone that has a cracked frame (or had, and fixed it) is: do you have a frame that GM had already "reinforced" in this area. If reinforced, on top of that location there will be a small metal plate, held in with two rivets (vertical), and also two of the bolts that hold the motor mount "stub" in place (horizontal). Those of you with big blocks, whether reinforced or not, have you experienced any cracks in the frame components in the engine bay, except those from the steering box of course?

    Trying to figure out if that small plate is all that is needed, or if by fixing that flex point, other problems crop up elsewhere.

    I'm thinking I may want to "box" the motor mount stub as best I can since it's already out, in addition to adding that GM riveted in plate. If the plate prevents any sort of cracking, even with say a big block, I'll probably just do that.
     
  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Sorry, not much help, but I believe my old crossmember matches your description. It was a CUCV M1008 and it was not cracked when I cut it out...
     
  3. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    My 80 K10 developed a crack on the right side of the engine cross member but I was thinking it was from the forward edge headed towards the back (about 2" long). I could be wrong about the location since I'm not home laying on my back /forums/images/graemlins/grin.gif . I welded mine and never had any more trouble from it. The truck had a very healthy roller 468 and saw a lot of abuse, no other cracks ever showed up.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    IIRC, the passenger side rear edge of the crossmember is flat, but on the drivers side, that rear edge has a "rib" in it for strength.

    I bet the drivers side has a flat forward edge, and if that is what happened on your truck, (right side is typically passenger side though, is that what you mean?) it probably did the same as mine...extended until it hit the base of that reinforcing "rib" of the crossmember.

    Did you drill a small hole at the very end of the crack before welding it? My dad is saying he read about that or heard about it from a welder before, yet another guy I know that welds for a living says its not necessary. Makes sense to me to drill it, seems about the same idea of shotpeening...removing a "stress riser". (open to any thoughts from welders here)
     
  5. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Mine was on the passenger side, like I said it's been a while plus the perspect is messed up laying on your back. /forums/images/graemlins/rotfl.gif

    I did not drill mine but i have heard that is the best way to repair a crack.
     
  6. m j

    m j 1/2 ton status

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    go to the wreckers
    that area was changed several times over the years
    the ones with the added brace also have thicker metal with a rolled edge
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Come on now, you couldn't just let me be blissfully ignorant that there was more than one way GM tried to fix this? /forums/images/graemlins/smile.gif

    I know what the plate looks like, the newer truck in the 'yard may be donating it's entire x-member to my truck. No point in welding up an inferior part when for the same time/money I can just replace it with something better. /forums/images/graemlins/crazy.gif
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Fixing this is really easy, build one out of 2" x 3/16 square tube and you can clear the cross over at the same time. /forums/images/graemlins/laugh.gif Or if you prefer to buy rather than build, MOO makes a bolt in.
     
  9. m j

    m j 1/2 ton status

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    does the MOO pick up the frame in as many places as the factory crossmember?

    I think stick welding the rest of the crossmembers in will stop the cracking as well.
     
  10. m j

    m j 1/2 ton status

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    x

    x
     
  11. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

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    my x memeber cracked and i needed x - over so i made this one . only thing is to make it a bit lower or something as i cannot get the pan off ...

    http://www.cardomain.com/id/k10andy
     
  12. 85m1009

    85m1009 1/2 ton status

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    [ QUOTE ]
    does the MOO pick up the frame in as many places as the factory crossmember?



    [/ QUOTE ]

    It attaches to the outside of the frame utilizing the three bolt holes that hold the bumpstop to the frame. It is also prepunched to drill two more holes in the bottom of the frame rail on both sides. A total of ten 3/8" bolts hold it into place plus bolts to the front of the motor mount brackets to tie it all together. /forums/images/graemlins/thumb.gif
     
  13. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    [ QUOTE ]
    Did you drill a small hole at the very end of the crack before welding it?

    [/ QUOTE ]

    not ona the truck side witht his comment, but here is my outlook on Stop Drilling. here is where i come from. 5 years experience of working on AH-1W Super Cobras and UH-1N/HH-1N Hueys as an airframes and hydraulics Mechanic. Stop Driling works about %80 of the time to actualy stop the crack. BUT this is with a patch OVER OR UNDER the crack. not welding it over and then re-enforcing it. So, my advice to you is this. drill it. only need a 1/32th inch bit or so and its done. make sure ya go in at the tip of the crack on both ends. if you are off a bit then it will not do any good, and that is where that %20 of failures is. from the knuckle dragger doing the drilling, not from the idea its self.

    i have a tiny crack on my steering box area and will be doing it some day.
    Grant
     
  14. m j

    m j 1/2 ton status

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    x

    x
     
  15. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I've read somewhere that the '85 on-up engine crossmembers are a design improvement over the older ones due to the cracking problems. I have also seen the '85 on-up to hae those little brackets to add bracing to them.

    Of all the '85 on-up vehicles I've worked on, I've not seen one crack anywhere on the crossmembers yet. /forums/images/graemlins/thinking.gif /forums/images/graemlins/wink.gif
     
  16. tarussell

    tarussell 1/2 ton status

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    My 1983 K-3500 had those extra braces on the engine crossmember too. I flexed/twisted and put more power to that truck than it should have ever seen and it never developed a crack with the later crossmember. I don't know when GM started using it but it does help and my 83 had it .
    I think that it would be worth swapping in a thicker braced crossmember. Tom
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Owners of K-trucks with cracked engine mounts/crossmembers(and BBC owne

    Pulled one out of an '85 K10 today.

    Rear edge is "rolled", and the additional riveted piece is in place.

    Sounds like those two improvements fixed the problem judging by the responses.
     
  18. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Re: Owners of K-trucks with cracked engine mounts/crossmembers(and BBC owne

    Good deal! I doubt you will ever have cracking problems now. /forums/images/graemlins/wink.gif /forums/images/graemlins/thumb.gif
     
  19. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Re: Owners of K-trucks with cracked engine mounts/crossmembers(and BBC owne

    Replacing them with the motor in is a BITCH though. I had to pull the motor on mine to get the new X-member in (I just cut the old one out). That is the reason why the MOO crossmember is bolted on from the bottom and outside edges of the frame. Good luck /forums/images/graemlins/thumb.gif
     
  20. 77ChevyK10

    77ChevyK10 1/2 ton status

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    I have a cracked frame from the steering box of course that has been fixed. My crossmember is also cracked all the way on the passengers side. I am just going to build a new one.
     

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