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4speed auto to 3 speed auto

Discussion in 'The Garage' started by frosty, May 31, 2004.

  1. frosty

    frosty Newbie

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    Hey, im looking to buy an 87 k5 its in real nice shape and at a great price, but it needs a tranny. it currently has a 4 speed auto and the guy says he has a 3 speed out of a suburban. can the two interchange? and would there be any problems w/ the swap?
     
  2. dremu

    dremu Officious Thread Derailer Premium Member

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    Four speed auto will be a TH700R4.

    Three speed could be a TH350 (if the Burb is a 1/2 ton) or TH400 (if it's a 3/4 ton.)

    Also depends on whether the Burb was 2WD or 4WD -- the Blazer is supposed to be.

    Point being that spline count on the tranny must match that of the t-case. You've also got the crossmember adapter length and driveshafts to consider.

    In short, do your homework first.

    -- A
     
  3. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Don't even mess with the 3 spd, Just get the Th700R4 rebuilt by a reputable shop with some of the standard upgrades and you won't have to worry about it for another 100,000 miles, at least. /forums/images/graemlins/whistling.gif
     

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