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transmission help

Discussion in 'The Garage' started by bigblazer433, Aug 4, 2005.

  1. bigblazer433

    bigblazer433 Registered Member

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    Well my tranny finally went out on me and i need some help on deciding what tranny to replace it with. Its an 87 Jimmy witha TBI 350 and a 208 t-case and the tranny is a 700 R4. So should I stick with the 700 R4 or go with something else.
    Oh ya the trucks on stock 10 bolts with 36" tsl's and I do only mild off road trails.
     
  2. chevy400hp

    chevy400hp Registered Member

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    well i go with a th400 if don"t mide giving up 4th gear.if you have to have 4th gear then i would say see if a 4le80 would work with your stock t-case
     
  3. R72K5

    R72K5 Banned

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    a th350 would pop right in place with no issues, a th400 would take driveshafts swap and adapter swap and so forth to make it work

    personally id have a th350 basic rebuilt and swap it in and be done

    good luck either way
     
  4. chevy400hp

    chevy400hp Registered Member

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    don"t get me wright i have th350 and i love it but i rather th th400 tuff sob and will just about any out there.
     
  5. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Stick with the 700. Just get a good rebuild and put the largest transmission cooler you can find on it. What's your gearing? Could be a reason why it went out. If it's geared 3.73 or something, I would regear to 4.56 or 4.88 for a little more power and you could use the OD. Since you do mild trails, don't worry about a TH400, use that one if you rag the hell out of it.
     
  6. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    I couldn't agree more...
     
  7. bigblazer433

    bigblazer433 Registered Member

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    my gears are 3.08's so should I swap in some 4.56's
     
  8. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    Good god YES!

    Remember, automatics rely on RPM's to keep them lubricated. As in your 700, the torque converter locks up when at speed. With your current setup of 36's, the 700's .70:1 final drive, and 3.08 gears, at 55 MPH you were turning roughly 1100 RPM's.

    That is really lugging the motor, plus it is not giving the transmission ample RPM's to build any kind of fluid pressure. Without fluid pressure, nothing gets lubricated, then it all comes apart.

    If you plan to keep the axles for a long time, go with at least a 4.88, if not a 5.13.

    If you plan to upgrade the axles later on for a larger tire, still go with at least a 4.88, but in the other axles install the highest gear (numerically) you can.
     

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