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A different sm465 vs th350 question. Please read.

Discussion in 'The Garage' started by Paxx, Jun 13, 2003.

  1. Paxx

    Paxx 1/2 ton status

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    If I was to use a th350 instead of the sm465 how low in the diffs would I have to go to equal/come close to the crawl ratio of the 465, if I had 4.56's in the diff's now?

    The reason I'm asking is because there is a 80 k5 for sale with a marine 350, th350, np205. 35" tires, new axles w/3.83? gears. The thing has almost no rust to speak of (very rare here in Canada) and the guy is asking $1600. The power windows, locks, and rear sliding window all work fine.
    Problem is that I was really looking forward to the crawl ratio of the standard but I found this truck in decent shape with the auto. I wasn't dead set against an auto so I wonder how close I can get to the crawl speed if I use lower diff ratio's. This is a DD though so it has to retain streetability. I'm hoping to be able to go a top speed of about 100km/hr - around 65mph which is the highway speed limit surrounding my city. It won't see much highway but in case there is a road trip (BB03 /forums/images/graemlins/thumb.gif) I want to be able to make it.
     
  2. blasterD

    blasterD 1/2 ton status

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    When figuring crawl ratio with an automatic you also need to figure in about 1.6:1 - 2:1 torque multiplication for the converter.

    Now: 465: 6.58:1 first gear
    205: 2:1 4x4 low
    gear: 4.56:1
    crawl ratio:60:1

    TH350: 350: 2.5:1 first gear
    torque conv: 1.8:1 Approximate
    205: 2:1
    gear: 4:56:1
    crawl ratio: 41:1

    You would need a 6.66:1 to keep your same crawl ratio.

    Or a doubler and a 3.33:1

    You can also get low gear sets from companies like TCI that give you a 2.75:1 first gear. Then you would only need a 6.06:1 gear but they tend to be pretty expensive unless you can do it yourself. I hope this helps.
     
  3. Paxx

    Paxx 1/2 ton status

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    hmm thnx I had no idea that the torque converter had a reduction in it. Thnx /forums/images/graemlins/thumb.gif
     

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