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4 seed Transmition and diffs for a 71 chev 3/4 ton 4x4

Discussion in 'The Garage' started by beatuptruck, Nov 27, 2004.

  1. beatuptruck

    beatuptruck Registered Member

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    Ok well I went to look at this truck today, its a 71 chev 3/4 ton 4x4 and it needs a lot of work, The transmition is not there and I was wondering what transmition will fit in it, SM420, NP435, or SM465? its an NP205 T-case, also what does the spline count have to be, I asume 10 spline, also the rear diff has been striped so I was wondering if I can just throw in a 14 bolt, also are front diffs interchangeble with the newer models?

    Any information would be helpful, thanks.
     
  2. Beast388

    Beast388 1/2 ton status

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    [ QUOTE ]
    Ok well I went to look at this truck today, its a 71 chev 3/4 ton 4x4 and it needs a lot of work, The transmition is not there and I was wondering what transmition will fit in it, SM420, NP435, or SM465? its an NP205 T-case, also what does the spline count have to be, I asume 10 spline, also the rear diff has been striped so I was wondering if I can just throw in a 14 bolt, also are front diffs interchangeble with the newer models?

    Any information would be helpful, thanks.

    [/ QUOTE ]

    As far as the transmission goes, by 1971 it was the SM465 if you wanted a 4spd. And yes, you will need a 10 spine NP205 to mate to it.

    14BFF are not a direct bolt-in but can be made to work with a bit modification. You will at least need to move the shock mounts on the axle to match the both-forward style used on 67-72 trucks. You might need to move the spring perches to the 40" depending on which 14BFF you get (3/4 ton or 1 ton). The 3/4 ton 14BFFs have a 42.5" spacing and 1 tons have 40.5". Some here on CK5 have used a 1 ton 14BFF without moving the perches by prying the springs outward a bit.

    The front axle is the easy part. Everything from '71 (1st year for disk brakes) up to '87(91) is a direct bolt in. The only thing to watch out for is the banjo bolt size on the brake calipers. D44's use a 7/16 banjo and the 10 bolts use a 10mm. You can do like I did and reuse the stock '71 D44 calipers on the swapped in axle whether it is a D44 or 10 bolt.

    Good luck in your search for parts! /forums/images/graemlins/waytogo.gif /forums/images/graemlins/waytogo.gif
     
  3. R72K5

    R72K5 Banned

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    if 4 speed then 465 since 68 and through 88 most models

    3 speed SM330

    auto th350 or th400, both happened, but mostly th350

    look on input shaft of the case and count the splines, this will tell us whether it was 4 speed(10spline), or 330/th350(27spline) or th400(32spline)


    if im wrong on any of that then lemme know, im 75% sure the 330 were 27 anyways

    axless would be dana44front and eaton/gm corp H072 7200lbs with 4.10 or 4./55front/4.57rear, no other ratios available in 67-72 K20

    14 bolt FF 10.5" for the rear would be the best for strength other than possibly a dana 70
    and dana 60 front would be the ultimate but the original 44 is plenty strong enough unless you go with huge tires

    it may not have factory axles uner it however, its hard to say without seeing,


    good luck
     

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