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Th350 to Th700-R4 swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JoseK5, Jun 3, 2002.

  1. JoseK5

    JoseK5 Registered Member

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    I'm ditching my Th350 in favor of a Th700-R4, I got an 89 which is supposed to be better than the pre 87 700's, I also got a B&M transkit , a Transgo shift kit, and a Painless wiring 4th gear lock-up kit. Other than the cabling and cabling brackets, do I need to get a special adaptor shaft, or any stock part from a different truck? What about 1350?? u-joints or some of those CV???? joints conversions?
    Thanks
     
  2. xnoahx

    xnoahx 1/2 ton status

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    ive been looking into this swap also and as far as i can tell the only thing that you might need is a different tailshaft for the trans from advance adapters if its the 2wd model. if its the 4wd model then you should be fine. You will also have to move your transfer case crossmember back about 2" cuz the 700 is longer. you driveshafts may need some work too if they are at thier limit but i imagine they would be fine
     
  3. Batmanjr

    Batmanjr 1/2 ton status

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    Um,
    Not to burst on your eagerness. But I'm currently droping a 205 behind my wife's 700 and if you already have the 205 behind the 350 and em going to put a 700 in front... Here is the major problem... The tailshaft (as previosly said) is 3 inches long versus the 7/8 inch long one from your 350. Thus extends the 205 out from your transmission 2 1/8 of an inch... The only way to currently compensate for this is to buy a $500 output shaft from AA to put into your 700r4, which means you have to rebuild your 700........ Fun Fun Fun... My solution is to locate a good machine shop locally and have them make you a spacer. It measures 6x6x2 1/8 inches. Drill a 4 3/4 inch hole directly in the center and four 3/8 inch boltholes in the corners exactly 4 inches away from each other. Thus giving you the adapter you need. If you have more questions concerning transfercase, let me know...
     
  4. Batmanjr

    Batmanjr 1/2 ton status

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    Re: Th350 to Th700-R4 swap *DELETED*

    Post deleted by Batmanjr
     
  5. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    You do not need a new steering column for that conversion. There is plenty of travel in the column for the 700 to work properly. You can also hit the wrecking yard and pick up the indicator to make things read correctly if you want.
     
  6. Batmanjr

    Batmanjr 1/2 ton status

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    So the stops for all four positions are not in the column itself past N? WHy does the shifter fall forward when in OD from Drive(3rd)? I need too know cause my wife's seems to not shift all the way into 1st...
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The detent is not in the column, it is in the tranny. If you take loose the bolt holding the shifter rod the steering column is free to move where ever.
     
  8. Batmanjr

    Batmanjr 1/2 ton status

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    But the actual handle moves forward when going from 3rd to OD on the column, I'm not talking shift positions, I'm saying what causes you to have to pull up on the shifter to move from OD to 3rd. What em I missing that would cause her 700 to act like a 350?
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I will have to check mine but I think you do not have the steering column adjusted properly. You should have to pull the lever towards yourself to get it past neutral and into reverse and park. Try having someone help you while you adjust the shift linkage. Loosen the adjustment nut and then have someone hold the shifter in the park position while you make sure the tranny linkage is in the park position then tighten the adjustment nut and try it again. Make sure the e-brake is on and also that you are on flat ground before doing this in case the truck decides to roll on you.
     
  10. Batmanjr

    Batmanjr 1/2 ton status

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    Thanks.
     
  11. mike reeh

    mike reeh 1/2 ton status

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    why cant you just shorten the output shaft? grinder/chopsaw

    mike
     
  12. Batmanjr

    Batmanjr 1/2 ton status

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    Because that only leaves you with about a half of an inch of spline going into the adapter. See the splines on the shaft start about 1/2 of an inch from the housing, thus the rest of the 3 inches is spline. About 2 1/2 inches. Thus if you cut off 2 inches, this only leaves a 1/2 inch of spline in your transfercase and your shaft won't bottom out right cause it's 7/8 of an inch deep, so you will still need an adapter to pull it tight. A spacer is cheaper and much easier to do.
     
  13. 95 Silverado

    95 Silverado 1/2 ton status

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    could you make the spacer 1/2" thick and cut the shaft, this would give you enough spline but shorten the total length?
     

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