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80+ TH350 trannys

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Erich_in_AZ, Feb 20, 2003.

  1. Erich_in_AZ

    Erich_in_AZ 1/2 ton status

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    OK, in my recent bout with my tranny, I got to calling around a few shops to see about rebuilding my tranny. More than one has told me that I don't know what tranny I have, or that it's been changed out. I think they are wrong, so I want to see what you guys think.

    According to them, the tranny on my 83 burb is either a 700r4, or in incredibly rare cases, a th350c (with the lockup convertor). Mine is NOT a lockup convertor. I know this, but they won't believe me. According to one shop GM didn't make a non-lockup th350 after 1980, so it was definantly swapped with an early th350, and had to have the output shaft changed.
    I think they are confused. Who's got non-lockup TH350's in their 1980+ chevys, or knows the deal with this?
     
  2. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I had a TH350C in my 1980 K20 (original trans). When it went my tranny guy asked me to find him a regular TH350 case. The lock-up was a good idea, but it was mainly designed for a car and not a full-size pickup. When I asked what year tranny to look for, he told me Pre-80 (I don't know if that meant everything 80 and above was a TH350C or not), but that might give you a better idea of what you are dealing with. Definitely put a good rebuilt non-lockup unit in and you should be fine.
     
  3. Erich_in_AZ

    Erich_in_AZ 1/2 ton status

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    Mine is definantly a non-lockup version. I just have a hard time beleiving that basically all of the trucks with a TH350/208 are lockup. Maybe I'm wrong?
     
  4. the professor

    the professor 1/2 ton status

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    Yea..they were all lock-up
    --
    There is absolutely nothing wrong with a 350c, it is identical to a 350 except for an aux. valve body to control the converter, and the lock-up converter itself
    --
    They handle the same amount of torque
    --
    The converters are usualy slightly higher stall, because they lock-up in hi gear...realy helps mpg
    --
    All TH350's are virtualy the same, except for valve body, acumulator and governor calibration..some for very small engines, had fewer clutches in the clutch pack..but all the parts will inter change...

    Virtualy every part in a 350c will fit in a 350, except the input shaft and front pump, case and valve body......

    Rebuilding you TH350 should be an non-issue
    /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
     
  5. Erich_in_AZ

    Erich_in_AZ 1/2 ton status

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    One tell tale sign should be the set wires going to the tranny for the lockup right? Does the TH350c have the extra part on the end of the input shaft like the 4L60's with the lockup TQ do? How can you tell the TQ's apart?
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    On the later ones (like the 700) as I recall, when you swap to a NON-TCC torque converter, you need to change the input shaft, as the TCC ones are either too long or too short.

    Don't know as there is an external way to tell if the torque converter is one or the other, but if you've got wires going to the tranny, (more than one, for awhile in the 70's at least, GM was using a wire from the tranny to control advance) or at least a plug for wiring, it's going to be a TH350C.
     
  7. R72K5

    R72K5 Banned

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    the lockup plug is white and square on most all of lockup trannies, and all 700r4 are lockup and have this plug, only two of the four pins on the plug are wired
     

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