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auto or manual tranny

Discussion in '40- & 55-Series Tech' started by cody, Apr 10, 2003.

  1. cody

    cody

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    doing a 350 conversion, need to get a tranny, just wanted your thoughts on what would be better, automatic or manual. kind of would like an automatic, but not sure on the ease of putting one in compared to lets say a sm 420 or 465. thanks
     
  2. nate77fj40

    nate77fj40

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    what type of use is your rig going to see? daily driver. mudding or rock crawling??
     
  3. cody

    cody

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    i live in san diego currently, and dont have too much time for playing, so primarily id use it on the road, but still would like a good tranny for playing in the hills, especially when i get back home. (washington state).
     
  4. Niner

    Niner

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    I currently have a th400 auto in mine. I would recommend the manual due to the fact that the autotrans is causeing heat problems for me.
     
  5. theo

    theo

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    With a manual you get a granny gear and better control on steep downhills using engine compression. You also get immediate throttle response (direct drive versus torque converter) and simple maintenance.

    With an auto, you don't need to clutch in the middle of steep climbs, but you can't control your descent as well without brakes. (Not a big deal to some people.)

    Autos take more effort to install (oil cooler, shifter, longer speedo cable, very short rear driveline, possible front driveline clearance issues), they cost more to buy and to rebuild (unless you do it yourself but how many people rebuild auto trannys at home?), and they are less dependable (IMHO).
     
  6. Slowerthanu

    Slowerthanu SILVER Star

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    I agree with you on a few of those points, but I will try to clarify a few other things. An Auto transmission is not less dependable if properly maintained, on that point, an auto tranny requires more constant maintanance than a manual. You will not need as low of gearing with an auto as the torque converter multiplies the torque by some amount (cant remember exactly how much). Most of the hardcore guys find 50:1 fine for an auto tranny vehicle and much more could require you to upgrade your braking system.

    After all of that, I would stick with a manual in an FJ-40, unless you enjoy hours of fabrication and possibly custom front shafts and/or a trimmed transmission pan.
     
  7. Erics75

    Erics75

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    Hey Niner, could you please elaborate on your heat problems, I was going to put a TH400 in mine.
     
  8. Gumby

    Gumby Supamod Staff Member s-Moderator

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    I like wheeling my auto tranny 80 series except on loose downhills when not touching the brakes is not an option. You can choose to try and keep the brakes from locking up or freewhelling the auto down the hill. Also, if your starter dies, or you have a battery problem, your day is done. You can always bump start a manual.
     
  9. theo

    theo

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    How's this for an unfounded rumor? The th400 is more prone to overheating than the th350. I tried to find where I read this and I couldn't. Anyone know if it's true?

    Here's another one. A friend of mine claims a rebuild on a 350 or 400 is not so tough; he's done several. The 700 is a different beast though. Don't try it until you have some experience and are willing to invest in special tools.

    Straighten me out here!
     
  10. nate77fj40

    nate77fj40

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    th350 and th400 are similar in rebuilds and not as complex as the 700. have done a couple of each and prefer the 350 or 400.
    i have also heard that too bout the 400 having some heating issues. all my buddies run th350's or manuals in their rigs and dont have any problems with them. one of my buddies runs a 454 big block 600Hp with a th350 behind no problems. i would gow ith the th350 if chosing an auto. IMO