third member switch

Discussion in '40- & 55-Series Tech' started by GaCruisin, Jun 13, 2005.

  1. GaCruisin

    GaCruisin

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    Im plannin on puttin 33's on my 79 and want some 4:11 gears. Is trading third members with someone the best way to get these gears? And how would the lower gears be on the road compared to the 3:70's?

    thanks
     
  2. eithegreat

    eithegreat

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    I'd estimate that your top speed would lower 10-15 mph from the 3.70 thirds. (I can easily cruise below 3k going 70-75 with 3.7's and 31's, but can only hit 60-65 with 4.10's. You'll get more oomph out of your truck (you'll even have to worry about spinning out sometimes) and will be able to go through all of your gears in a short fraction of the time compared to 3.7's... I don't know what the exact compensation of 33's will have, I'd say they tack another 5-10 mph...
     
  3. bad_religion_au

    bad_religion_au

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    4.11:1 was made for 33's

    you'll love it
     
  4. Gus

    Gus SILVER Star

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    Sort of a hi-jack; I've been thinking of doing this to my 79 FJ40, would you have to use fine spline third member diffs out of a 78 FJ40 or FJ62 or could you use the (from what I've heard, weaker) course spline third members providing you switched to course spline axle shafts.
     
  5. bad_religion_au

    bad_religion_au

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    i don't think the coarse spline diffs from 76-78 ( i might be wrong) were coarse axles, weren't they coarse pinions?

    i don't know... the full floaters are fine spline after 76
     
  6. nuclearlemon

    nuclearlemon not an addict Moderator

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    when you swap, swap slipshafts also, that way neither you or whomever you swap with will have to deal with matching flanges to driveshafts.

    i went to 4.11's in my 60 when i went 33s and i'm almost back to stock.
     
  7. eithegreat

    eithegreat

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    A '75 I had (as with my newer 40's) was fine axle, it was stock as well. Also, what you can do is just change out the spider gears, right? I thought that only the older FJ40's had course axles?
     
  8. Yoda

    Yoda

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    My 71 has the fine axles OE and the coarse pinion.
     
  9. nuclearlemon

    nuclearlemon not an addict Moderator

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    when discussing fine vs. course on later model 40's they're usually talking about the pinion, not the axles.
     
  10. Gus

    Gus SILVER Star

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    This sounds easier than I had anticipated, thanks for the clarifying everyone ,
     
  11. PabloCruise

    PabloCruise SILVER Star

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    If you can find fine spline pinion thirds from a 62 (4.11), that would be the ticket.

    Also, put the front third in the rear, as they have virtually no mileage compared to the rear...
     
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