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'78 or '84 axles

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by horsepit, Jan 10, 2002.

  1. horsepit

    horsepit Registered Member

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    \'78 or \'84 axles

    I'm looking at two set of 3/4 ton axles (14 bolt FF and Dana 44s). One came out of a 1978 pick up (4.10) the other out of a 1984 Suburban (3.73). Any benefits from either?

    1987 Blazer, TH700R4, NP208, 3.42, Rancho 4", 33"
     
  2. TorkDSR

    TorkDSR 1/2 ton status

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    Re: \'78 or \'84 axles

    well obviously not, so just send the 4.10 my way and ill make sure that there's no way you can use them[​IMG]

    but seriously i think gearing wold be the only. the both take, to my belief, the same brakes and calipers etc

    beligerence doesn't justify intelligence.
    <font color=blue>wheelers hate posers.</font color=blue>
    <font color=red>79k15/400/700r4/205/38.5</font color=red>
     
  3. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: \'78 or \'84 axles

    If they are actually out of 3/4 ton trucks, then here is what they probably actually are (if stock).

    '78 - 14FF rear, front is probably a 10-bolt but could be a carry over Dana 44.

    '84 - most I have seen had the 14 semi-floating rear axle, front would definitely be a 10-bolt if stock
     
  4. horsepit

    horsepit Registered Member

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    Re: \'78 or \'84 axles

    These are straight bolt ins correct?

    1987 Blazer, TH700R4, NP208, 3.42, Rancho 4", 33"
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: \'78 or \'84 axles

    Yep. Rear driveshaft will require combo u-joint.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Re: \'78 or \'84 axles

    I have an "89" blazer that is stock height now. I am going to lift it 6" and install the 14bff rear. Will i need to lengthen the rear driveshaft or will the difference between the 10b and the 14b center of housing to center of u-joint be enough to compensate for the extra needed length? There is a 5/8" difference between the two. 14b being longer center to center.
     
  7. pcorssmit

    pcorssmit 1/2 ton status

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    Re: \'78 or \'84 axles

    I think the '80s 3/4 burbs had the 9 1/2" semi floating rear. If you're gonna go 8 lug anyway, might as well get the 10 1/2 full floater.

    '78 most likely had a 10 bolt front. Could go either way, though, it was a transitional year. '84 will definitly have a 10 bolt front. Not really any better/worse than a 44.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: \'78 or \'84 axles

    I have never owned a Blazer so I don't know for sure. I have put 6" lifts on trucks before, longboxes, without a different driveshaft. On a shortbox truck, I think you'd probably need one.

    As for the 5/8" of difference with the floater rearend, you need more than 5/8" anyway, and I honestly have never noticed that little bit anyway when swapping from 10 bolt to 12 bolt and finally now to 14 bolt semi floater rear. I am swapping in the full floater so I might notice it more--but by then I'll have removed my current shaft because my truck will have a 4 speed/205 combo.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  9. woody9

    woody9 1/2 ton status

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    Re: \'78 or \'84 axles

    in the 4 what it's worth department...
    I put a set of 80 3/4 ton 14FF/10B Front 4:10s under my 91 1/2 ton sub. ONly issue is/was the parking brake. Gained a TON of braking capability (up from 11 to 13" in rear... but those drums weigh 2 tons each!!!)
    Had to use the custom joint (NAPA 447 i believe) Going to try disk's on it come spring and collecting parts now, so not sure the ultimate fix on e-brake.
    Checked the 'effective length' of the rear by marking flange across to axle on old 10 bolt.. and comparing to flange on the 14FF. No difference. D-Shaft worked great!

    Now to figure out what to do with the old 10 bolds? and tires/rims!!??!!? (9.50 BFG ATs used 10 months!! on 8" rally rims!)
     
  10. pcorssmit

    pcorssmit 1/2 ton status

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    Re: \'78 or \'84 axles

    Its really hard to say when a longer drivshaft will be needed for sure. It depends on so many things, ie total length, angle, whether the t-case is dropped, how the rear is lifted, that it really has to be determined on an individual basis. FWIW, my stock shaft worked out OK on the 14FF, I have the u-can't-affford-it shackle flip using the stock springs and stock hangers. The slip yoke is a little farther out of the cast than stock, but not enough to cause concern.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     

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