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rear end swap

Discussion in 'The Garage' started by mrmojo32, Sep 13, 2006.

  1. mrmojo32

    mrmojo32 Registered Member

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    I have an 89 GMC Jimmy with a 350/4 speed to 10 bolts front and rear. I am also running 35" tires. I am in Louisiana so all the off road is mud.

    I am thinking about upgrading to a 14 or 12 bolt. I have 2 questions:

    What gear ratio does everyone recommend?

    If I went to a 12 or 14 bolt, what years would match mine? Also, are truck rear ends the same as for Blazer/Jimmy? I have never done an axle swap so I am wondering what will bolt up easily.

    Thanks for any feedback in advance. :rolleyes:
     
  2. mrmojo32

    mrmojo32 Registered Member

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    ?

    Anyone? :confused:
     
  3. thfonz98

    thfonz98 1/2 ton status

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    wont comment on the rest as i still have my 10bolts but a 12 bolt isnt much of an upgrade. Go 14 bolt.
     
  4. big dan

    big dan 1/2 ton status Premium Member

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    14 bolt all the way. 12 bolts are not really strong enough to make the swap worthwhile. any 3/4 ton 14 bolt from 73-87 will be almost bolt in, minus the conversion u-joint and new u-bolts. there are other years that fit I think but I dont know which ones.
     
  5. mrmojo32

    mrmojo32 Registered Member

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    ok

    So truck axle assembley's of those years fit my '89 Gmc Jimmy... right?

    Also any ideas on gear ratio with the set up I have and goign mostly mud?
     
  6. BulldogK5

    BulldogK5 1/2 ton status GMOTM Winner

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    Go with the 14b. The years listed will work. A ff from a 3/4 ton suburban or truck will be a direct bolt in, a 1 ton will require moving the spring perches. As for gears it depends on your tire size. If you stay with the 35's then 4.10 to 4.56 will work. If you plan to go bigger you will need lower gears. I run 39.5's with 4.10's for now, I am waiting to upgrade to a 5.13 ratio for some get up and go. Your front 10b will need to be changes out to an 8 lug setup or use a spacer/adapter for the rear to go with a 6 lug pattern.
     
  7. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    what ratio are you running now? most of the stock 14 bolts I have seen in my area were 3.73, 4.10, or 4.56 ratios. 4.10 would probably be the best of both worlds if you are still driving it on the street since you do not have an overdrive. I know a lot of people will disagree with me but a 700R4 would be nice with 4.56 gears. that way you will have a really deep first gear(3.06:1) and overdrive to compensate for the 4.56. Look for a 3/4 truck and get both axles. the dana 44 is worth the proper bolt pattern alone.
     
  8. cbbr

    cbbr 1 ton status GMOTM Winner

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    Yep. But if you are going to play in mud the 4.10 will do just fine with 35's.
     
  9. mrmojo32

    mrmojo32 Registered Member

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    I have 10 bolt now and I think it is 308. The transmission is a sm264 or something. It is a 3 speed standard with a L gear. The .350 motor has only slight modifications.

    [​IMG]
     
  10. Clod_King

    Clod_King 1/2 ton status

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    That's a nice lookin' truck man. I'd say go 14 bolt. I don't own one, but i do own a 12 bolt, and I hate it.
     
  11. mrmojo32

    mrmojo32 Registered Member

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    Rims

    I wonder if I will be able to find those kind of rims in 8 lug pattern. I know the rear axle is shorter than the front so maybe an adapter would be better.
     
  12. KGsK5

    KGsK5 1/2 ton status

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    are there adapters that will convert the 8 lug of a 14 b and a d 44 to the 6 lug?
     
  13. Gravel Maker

    Gravel Maker 1/2 ton status Vendor

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    14 bolt is the only way to go.....

    don't mess around with something you won't be happy with....
     

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