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trans question

Discussion in 'The Garage' started by bronc3buster842001, Nov 26, 2006.

  1. bronc3buster842001

    bronc3buster842001 1/2 ton status

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    pulled the tranny from a 2wd parts truck the other day. at first i thought it was 400 by the shape of the pan but on it has writing on it saying its from an 86 with a 4.3 and below that it says its a 375 . ive never heard of these so some info would be helpful. also the tailshaft housing bolts on like a 400
     
  2. 383whiteblazer70

    383whiteblazer70 Registered Member

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    Would help to know what year,make,model donator is,what engine its got???
     
  3. bronc3buster842001

    bronc3buster842001 1/2 ton status

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    it come from an 86 chevy with a 4.3
     
  4. 383whiteblazer70

    383whiteblazer70 Registered Member

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    midsize or fullsize blazer,pu,???
     
  5. bronc3buster842001

    bronc3buster842001 1/2 ton status

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    fullsize pickup
     
  6. 383whiteblazer70

    383whiteblazer70 Registered Member

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    is it a auto 4 speed/od
     
  7. bronc3buster842001

    bronc3buster842001 1/2 ton status

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    its just a 3 speed it looks just like a 400
     
  8. MaxPF

    MaxPF 1/2 ton status

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    When you say it has writing on it do you mean actual handwriting, written with a paint pen? If so, it is probably a junkyard tranny. In that case, I don't know what the 375 refers to. GM did make a THM375 - it was a light duty 400 with a different tailshaft and tailshaft housing designed to use a TH350 yoke. Externally it would appear identical to a 400, except the tailshaft housing will be marked "375-THM". Since these trannies were only used from 72 to 76, and then only in passenger cars, I find it extremely unlikely that you have one of those. Then there is the later THM375B, which is a HD TH350, and looks identical to a TH350. Since you said the pan looked like a 400, then it probably isn't one of these. Most likely it is a standard 400, although why they would put that behind a 4.3 is puzzling to me... Anyway, check the TS housing and count the number of splines on the output shaft. If you count 32 splines, then it is probably a 400.
    Pics would be helpful, too :wink1:
     
  9. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    As far as I know those trucks came with an overdrive trans, prob a 700 but possibly a 200. Shift the detent by hand, has it got 7 positions? p,r,n,o/d,d,2,1.
     

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