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Technical Lowering my ‘66 GMC Shop truck

Discussion in 'The Hokey Ass Message Board' started by nitrousnutter, Jan 24, 2020.

  1. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

    nitrousnutter
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    I hope I’m not going to get shot down in flames here, I’m over in the UK and have a ‘51 mega project that will get done one day but it’s far from there. I also have this as my beater it’s a ‘66 GMC C10 which I love, has a 355 sbc, currently running the standard three speed and standard rear end, I am looking at fitting an NV3500 which I happen to have and then a better geared rear end as now she screaming at 55mph.
    [​IMG]
    [​IMG]

    As you can see she standard height which is fine but would love to lose a couple of inches, I’m also thinking of adding 2.5 drop spindles and disc brakes, so my question to all you clever Hambers is when I’ve measured up the rear shackles do the ones that drop it 2 inches measure 4 inches longer because I only have about three inches between the top of the shackle and the bed floor as shown below

    [​IMG]
    [​IMG]

    Getting parts is a pain as have to ship them over here have any of you good people lowered a leaf sprung C10 with these and had clearance issues?

    Many thanks Jason


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  2. treb11
    Joined: Jan 21, 2006
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  3. Colin HD
    Joined: Sep 14, 2008
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    Sweet looking ride.
    Is the axle on top or below the springs?
    Already fitted with lowering blocks?
     
  4. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

    nitrousnutter
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    It’s below the springs but an axle flip will drop it too much and I’ll need to c notch the frame, wanted to lose a couple of inches but not have any major headaches to keep it semi running while I do it as show season will soon be on us and I use it to tow my trailer tent to the shows, that’s another reason as the trailers at a bit of an angle the way it is. Just wondered if anyone has fitted the extended shackles to drop one


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  5. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

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  6. Chavezk21
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  7. nitrousnutter
    Joined: Aug 23, 2011
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    thanks some very good reading there


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  8. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

    nitrousnutter
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    Do any of you know if the extended shackles will hit the floor on my C10?


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  9. Colin HD
    Joined: Sep 14, 2008
    Posts: 274

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    Would almost guarantee it, as you've got so little clearance to start with.
     
  10. Colin HD
    Joined: Sep 14, 2008
    Posts: 274

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    I would probably pull them apart and de-arch the springs.
    Could do it in a day, then back on the road.
     
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  11. nitrousnutter
    Joined: Aug 23, 2011
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    Cool is de arching something that is easy to come? Never tried it before


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  12. Roothawg
    Joined: Mar 14, 2001
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    I have a guy that works for me that has a lowered 65. He has experimented with everything. I’ll ask him Monday.
     
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  13. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

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    Thanks Roothawg, only want to lose a bit of altitude no frame alterations if I can help it.

    Thanks again mate
    Jason


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  14. Roothawg
    Joined: Mar 14, 2001
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    I wanna say his is a coil spring setup though.
     
  15. Yes, Mike’s 65 is coil spring rear.

    As mentioned in the other referenced thread, longer shackles drop it roughly 1/2 the distance of the shackles because of only moving one end of the spring up.

    I would make sure to measure well as it seems you are to make sure there is enough clearance before getting too long of shackle. I have never lowered the rear of a leaf spring rear on that body style, but have done plenty of coil spring rears on the Chevrolet’s. Depending on how the front spring hangers are attached to the frame, you may be able to move them up or possibly flip them over and switch side to side to get more drop as well. I have done that on several leaf spring trucks in the past.
     
  16. It’s not hard, but takes some time. It is easier to pull a few leaves, but that also softens the ride and limits what you can haul. If you are going to the trouble of de-arching, I would just reverse the arch of the main leaf which ultimately reversed the eyes where it mounts. Typically, that will drop it 1-1/2” or so in itself.
     
  17. I would get an actual measurement on the extended shackles and compare to yours. Looks like you could likely only go another 2-1/2” longer and not hit the bed floor. However, that and reversing spring eyes would get you the total drop of 2-1/2” or so you are looking for.
     
  18. mickeyc
    Joined: Jul 8, 2008
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  19. mickeyc
    Joined: Jul 8, 2008
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    Springs? The c10 I have of that vintage has trailing arms and coil springs. Did I miss something? Did GMC use a different system than Chevy?
     
  20. Yes, GMC are leaf springs all the way to 72 (I think) where the Chevrolet’s are coil spring through those two body styles.
     
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  21. mickeyc
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  22. mickeyc
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    Ah, therein lies the difference.
     
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  23. Roothawg
    Joined: Mar 14, 2001
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    I never knew that.
     
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  24. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

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    Yes mickey totally strange concept both are so similar but apparently GMC were the luxury truck with leafs and a slightly different interior everything else is the same as far as I know


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  25. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

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    I’ve now found online that Western Chassis do a set of springs -2 front coils and -4 rear leafs for 63-72 c10’s I’ve emailed to see if they go on without modification to the frame


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  26. I used drop spindles and 2.5 dropped coil springs for the front, and CPP performance rear 4" drop leaf springs on mine. Still rides well and can carry a load. No frame mods needed.
     
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  27. I know you said it's too low for you, but I thought I'd say that a c notch is not needed. I flipped the axle on my 66 c10 and don't have any problem without a c notch. Maybe on a really big bump it will hit the bump stops but since I try to avoid pot holes it almost never happens. It also only took me a day or two, so you wouldn't be missing shows much if you did it. I get that you said you don't want to go that rout, but I just thought I throw this out there.
     
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  28. Roothawg
    Joined: Mar 14, 2001
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  29. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

    nitrousnutter
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    That’s exactly what I wanted to hear, I see western chassis do a kit of springs (front coil rear leaf) but their drop spindles are a bit pricey, there’s a firm called Toms Classic on eBay who do a drop spindles kit with four pot callipers braided lines and drilled and grooves rotors a lot cheaper than western chassis, I believe it’s using McGaughy drop spindles so hopefully good quality although not sure on the callipers they look a bit cheap Chinese


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  30. nitrousnutter
    Joined: Aug 23, 2011
    Posts: 236

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    Thankyou that’s worth bearing in mind incase I do get brave and go that route


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