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TH350 / TH700R4 Swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazer_Boy, Dec 18, 2000.

  1. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    I have an '81 Silverado with a 350 out of a '78 Cheyenne and a bum TH350 :(. I have the oppurtunity of replacing it with a TH700R4 (it's free by the way and is a Goodwrench). I've been by some that this combination will not work because of the gear ratios (poor performance, mileage...). The transfer cases are geared the same but it has the 12 bolt rear axle. The first year of overdrive trannies ('82) from what I have seen in my '82 uses the ten bolt axle. Will this work or are there some ratios that need to be changed and if so, where.
     
  2. JimmyDie6.2

    JimmyDie6.2 1/2 ton status

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    who told you about "gear ratio problems". What gears are in your truck??? 2.73s? 4.11s? what size tire??? I believe the output shaft that bolts to the T-case from the 7oo and the 350 trans have the same number of splines so your good there, the lengths are different. the steeper your gears, like 4.10s, the better your 700 will work.................js
     

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