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Is it safe to re-drill spring pads to move axle back?

Discussion in 'The Garage' started by 88jimmy4x4, Jan 17, 2004.

  1. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    I recently did an axle flip and it caused my rear diff to move forward and now I have clearance problems, plus it looks weird. I think it moved about 1.5" or so...not sure. I know some have re-located their rear diffs back by drilling a new hole further up on the perch...is this safe for a daily driver? how much forward should/can I do this?

    I know I could get the zero rates and re-locate but I finally have the Jimmy sitting at the desired ride height so I was considering drilling.

    whatcha think?
     
  2. Triaged

    Triaged 1/2 ton status

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    Personally I never liked the idea of redrilling the center pin hole in the leaves. They like to fail without extra holes in them /forums/images/graemlins/crazy.gif

    Redrilling the axle perch is the best way to go. They are easy to drill and there is only 2 holes. Some center pins are different sizes so double check before you drill...mine were 9/16" but most are smaller. You will also have to knotch out the u-bolt plate for the top of the center pin to fit. 1.5" might be pushing it...but you will have to make that call based on how much room you have on the spring perch. I moved mine back 1".
     
  3. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    yeah, i have my rear axle moved back an inch, and my front moved forward an inch. Both use offset holes in the perches. 1.5" is prolly pushing it... but 1" is definitely do-able.

    j
     
  4. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    Thanks guys, 1 inch will be fine and way better than what I have now. Anyone got a picture of the u-bolt plate notch I need to cut?
     
  5. therobzilla

    therobzilla 1/2 ton status

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    John,

    I have redrilled both my front and rear springs, and I run Jeep Wrangler front main leaf springs with a custom pack under the main leaf. I have redrilled both my front and rear packs, and I absolutely pound the living $hit out of my blazer, and I have no spring clamps on the front spring and flex the $hit out of them also. To date, and you can ask anyone that wheels in the AZ, I have yet to break a spring, front or rear....

    I don't see any problems with this at all on a daily driver. Like I said, I wheel the $hit out of my junk and have had no problems.

    If you would like there are some pictures on my webshots of my blazer front springs really flexed and these have been redrilled without incident.

    Rob
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    First off, I have seen Rob's front main leafs bent almost 90 degrees at the perch when we were on Upper Helldorado. I thought for sure that spring was gonna break and it never did. (Get some clamps Rob...LOL)

    My 57" rears are re-drilled through the leafs...1.5".

    My D60 front is moved 1.25" with the redrilled perch and clearanced spring plate.

    I haven't had any trouble at either end.

    Rene
     
  7. Triaged

    Triaged 1/2 ton status

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    [ QUOTE ]
    John,

    I have redrilled both my front and rear springs, and I run Jeep Wrangler front main leaf springs with a custom pack under the main leaf. I have redrilled both my front and rear packs, and I absolutely pound the living $hit out of my blazer, and I have no spring clamps on the front spring and flex the $hit out of them also. To date, and you can ask anyone that wheels in the AZ, I have yet to break a spring, front or rear....

    I don't see any problems with this at all on a daily driver. Like I said, I wheel the $hit out of my junk and have had no problems.

    If you would like there are some pictures on my webshots of my blazer front springs really flexed and these have been redrilled without incident.

    Rob

    [/ QUOTE ]

    I still never liked the idea of extra holes drilled into the leaves...that is one of the biggist things I have against the 57" fords and why I would stick with 56" chevies if I was to do that (but I'm not because I have some 63" chevies to put on). I had 2 leaves in my stock pack crack right at the center pin hole. Chris from the SoCalBigDawgs (who was in TTC this year) has broken way to many stock 52" chevies (I know he has gone through at least 4 spring packs!). I'm sure most people don't have a problem with doing it but I just don't see a good enough reason to do it...not to mention that leaves are a bitch to drill through! I also always run spring clamps (and am even thinking of adding some more to my front leaves!). Maybe I am too anal but a broken leaf can be one of the hardist things to get off the trail with.
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I gotta say I agree.

    Lots of people seem to get away with it, but I'm not comfortable with the idea. I've made a couple of offset plates for my front axle 2" offset (think zero-rates) and I've redrilled perch/plate for smaller offsets. Personally, I refuse to redrill springs. Of course, some people are not comfortable with zero rates (particularly in the front) but I don't think my little 1/2 x 3 x 6" offset plates are going to be a problem. <shrug> I guess it mostly depends on your comfort level. But for a street rig, I would really try to avoid redrilled springs (especially front) just due to the danger presented to you and others should a main spring break at the edge of the perch at 60+ on a crowded freeway or highway (with no median /forums/images/graemlins/eek.gif ).

    FWIW, Rob does carry spare main leafs... And I thought I remembered hearing of him having broken one, but maybe that wasn't one of the redrilled ones...
     
  9. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    Thanks for the replies /forums/images/graemlins/thumb.gif
    Makes it difficult to decide what to do. I know the spring material must be hardened or something cause I tried to trim a little off the ends of a AAL with a sawzall and couldnt do it. I could drill the springs with a drill press at work or notch the u-bolt plate at work as well. Im not crazy about doing either but I must do something. I just need to decide because there seems to be drawbacks to both.
     
  10. Triaged

    Triaged 1/2 ton status

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    There are far less drawbacks to drilling the perch. The nice thing about it is that you can go back to stock real easy if you don't like it. The spring wouldn't notice the extra hole in the perch...in fact some perches (i.e. the cast 14FF) arn't flat on the top anyway. That was part of my reason for making new perches.
     
  11. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    [ QUOTE ]
    There are far less drawbacks to drilling the perch. The nice thing about it is that you can go back to stock real easy if you don't like it. The spring wouldn't notice the extra hole in the perch...in fact some perches (i.e. the cast 14FF) arn't flat on the top anyway. That was part of my reason for making new perches.

    [/ QUOTE ]


    The only thing I worry about in drilling the perch is the amount of "seat" on either side of the new hole....

    It seems that if the hole got too close to either edge of the perch, the axle might be more likely to "spin"??? I'm trying to visualize it, and I know that there are still 2 U-Bolts clamping down hard on the perch, so the entire perch is still 100% touching the underside of the spring.

    ... I guess it just gives me a weird "feeling" knowing that a centering pin is not "centered" anymore on the perch??? /forums/images/graemlins/crazy.gif
     
  12. marv_springer

    marv_springer 1/2 ton status

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    [ QUOTE ]
    The only thing I worry about in drilling the perch is the amount of "seat" on either side of the new hole....

    It seems that if the hole got too close to either edge of the perch, the axle might be more likely to "spin"??? I'm trying to visualize it, and I know that there are still 2 U-Bolts clamping down hard on the perch, so the entire perch is still 100% touching the underside of the spring.


    [/ QUOTE ]

    Well, nobody wants a main leaf breaking while they're sailing down the hi-way /forums/images/graemlins/eek.gif, so this is a serious issue.

    The center pin is in pure shear (if the U-bolts are tight) and can support no resistance to torque - and so it's position on the spring pad would not affect the performance of the U-bolt connection.

    What is an issue is that any hole in the leaf spring (stock or bootie fab'd) is a stress riser and will lead to a fatigue break after some bending cycles. So the meat of the matter is: does your setup have a "center pin hole" oustide (or near the edge) of the "U-bolt Clamped" area so that the spring experiences bending stress in that location. If so.... it WILL break!

    This dangerous scenario could possibly be reached by all three methods mentioned in this thread (or a combination of two or more): 1) Zero rate, 2) re-drilling the spring, and 3) offset drilling the pad.

    That being said, you should have a safe setup.... if your hole(s) stays well within the clamped area of the U-bolts...

    Marv

    * Edited *
    BTW, there's nothing magical about the stock arrangement (center hole in the middle of clamped area)... You still have a stress riser (hole) in the clamped area of the U-bolts - and it works good because the bending stress (and movement) doesn't penetrate that far into the clamped area. Those who have experienced broken 52's have prolly had either really old springs, loose U-bolts, or "convexed" axle pads (or a combination of all) to allow the movement and stress to get to the hole.
     
  13. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Agreed. I should have mentioned that my offset-plates are longer on the offset side to help stabilize the new pin location which otherwise would be close to the edge of the perch.
     
  14. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    Marv, just to point out a fact here....
    How many springer setups, all of the ones i have seen have been through a lot of use(including brians burban even though it has never been offroad) have broken a redrilled pack?

    the pack is also set within the limits of the clamps.
    like stated before, i think so long as the u-bolts are tightened correctly and the unused hole stays inside the clamped area, you should be fine.
    Grant
     
  15. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    Well whats the solution to this?
    I know alot of members have a flip and I searched and researched before I did the flip and never read anything about flips causing the axle to move forward so this kinda caught me by surprise. If the ride wasnt so dang good I would go back to rear leafs and no flip /forums/images/graemlins/confused.gif

    What did everyone else do?
    Just trim the front of the quarter panel to open it up more?
    I really hate shortening the wheelbase.
     
  16. marv_springer

    marv_springer 1/2 ton status

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    [ QUOTE ]
    marv, just to point out a fact here....
    How many springer setups, all of the ones i have seen have been through a lot of use(including brians burban even though it has never been offroad) have broken a redrilled pack?

    [/ QUOTE ]

    I have yet to see any "Springer" equipped trucks break a leaf.... Hell, I ran around w/ the first set of offset drilled springs under the back of my Blazer for ~5 years before I sold it. Oh... and before that - I too was a suffer-er of broken 52" leafs/forums/images/graemlins/confused.gif....

    [ QUOTE ]
    Well whats the solution to this?
    I know alot of members have a flip and I searched and researched before I did the flip and never read anything about flips causing the axle to move forward so this kinda caught me by surprise. If the ride wasnt so dang good I would go back to rear leafs and no flip /forums/images/graemlins/confused.gif

    What did everyone else do?
    Just trim the front of the quarter panel to open it up more?
    I really hate shortening the wheelbase.

    [/ QUOTE ]

    The "shortening effect" happens to pretty much everyone who does the flip. Any or all of the options discussed in this thread could be used to correct it. Just don't go too far. /forums/images/graemlins/crazy.gif

    Marv
     
  17. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    [ QUOTE ]
    I have yet to see any "Springer" equipped trucks break a leaf.... Hell, I ran around w/ the first set of offset drilled springs under the back of my Blazer for ~5 years before I sold it. Oh... and before that - I too was a suffer-er of broken 52" leafs....


    [/ QUOTE ]
    point made.
    thanks. i think others will thank you as well.
    Grant
     
  18. Triaged

    Triaged 1/2 ton status

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    You sold the K5 /forums/images/graemlins/eek.gif Now what do you drive?
     

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