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How to determine rear leaf size for lift?

Discussion in 'The Garage' started by JohnHenryDoe, Nov 22, 2005.

  1. JohnHenryDoe

    JohnHenryDoe Registered Member

    Nov 15, 2005
    Likes Received:
    I have a lift on my 87 GMC; not sure how to determine it's size. When I bought it I was told it had a 6 inch lift. The front springs are 9 total leafs; the back is 5 leafs plus 3 1/2 inch block. Frame height where bumpers attach is 27 F 29 R.
    I have to remove the block for inspection purposes, but the lift can stay; I either need to add leafs to the rear pack or get another set of rear springs.
    To equal the front, I need to know how to calculate the size spring for the blockless rear.
    I have though of pro-comp add-a-leafs but don't think they would get me enough rear height.

    Any help is appreciated :bow:
  2. Brocky

    Brocky 1/2 ton status Premium Member

    May 22, 2005
    Likes Received:
    St.John's Newfoundland, Canada
    Lose the block in the rear and get a Shackle Flip from Diy4x or Off Road Design. That will give you 4 to 4.5 inches in the rear. Its ok to have it a bit higher in the back. You dont want to add anymore leafs, it will be too stiff. www.diy4x.com/suspension.htm or www.offroaddesign.com
  3. 6.2puller

    6.2puller 1/2 ton status

    Jul 8, 2004
    Likes Received:
    New England
    §10.5.11 Suspension lifts are permitted provided that they are manufactured by an after market manufacturer, are designed for the make and model vehicle on which it is installed, is installed according to the manufacturer'’ recommendations, and as long as the entire kit is used.

    §10.5.12 No lift kit which utilizes lift blocks between the leaf springs and the axles or which uses spring shackle extensions may be installed on a vehicle. Only original equipment blocks are permitted.

    I wonder if the shackle flip will be considered a shackle extension in Maine?
    Atleast your troubles are becoming less and less as you get educated on what Maine allows and doesn't :wink1:
  4. thatK30guy

    thatK30guy 1 ton status Premium Member

    Jan 12, 2001
    Likes Received:
    9 leaf front springs? Sounds like the old discontinued Rancho Mud Bogger springs which are a firm riding set.
    I've got a set of these springs sitting in my shop for "collector" items as they were popular back in the 80's and 90's but phased out to softer riding springs.

    Can you take a picture of the front springs? If so, take a pic of the forward spring eyes as the Rancho's should have a military wrap around the main spring.

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