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I have trans. questions too.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Rollingthunder, Apr 12, 2001.

  1. Rollingthunder

    Rollingthunder Registered Member

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    I was wondering if ya'll can tell me the main differences and good points about both (along with the bad ones) the TH350 and the and TH700? Also the same thing with the 205 and 208 cases.
     
  2. '73 K5

    '73 K5 1/2 ton status

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    TH350 is a good 3 speed auto with no overdrive. The 700R4 is a 4 speed auto with the overdrive. Pretty bad reputation around here. They grenade all the time when combined with towing and/or offroading. NP205's are really strong cases with a really good rep. The only bad thing is they don't have a really low, low gearset. The NP208 has better gear reduction but its aluminum case, weaker...they are supposed to do OK if you keep it full of clean ATF, whereas I've run my 205 forever with mud and water floating around in it with no probs.

    '73 K5
    Chevy good...Ford bad
     
  3. 84K5WITHAJUNK305

    84K5WITHAJUNK305 Registered Member

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    The TH350 is an extremely tough 3 speed auto, the 700r4 is a decent transmission(the excepting is the first three model years of 82-84) as long as it's kept cool(get the biggest tranny cooler you can and then mount a fan on it), and isn't abused. I've been told that keeping the ATF around 140 degrees is optimum. The 205 is legendary because of it's all gear driven design being almost unbreakable, it's got a cast iron case and weighs about 170 pounds, while a 208 is a chain drive and has an aluminum case, it's not as strong, but weighs about 100 pounds less. The 700r4 has lower 1st and 2nd gears than the TH350, and also has an overdrive. The NP208 case has a low range ratio of 2.61:1 and the 205 has a low range of 1.96:1. Oh, I forgot, the aluminum case is actually stronger(in terms of holding the internals in place), but it's more prone to crack if hit by a rock(which shouldn't happen with the proper skidplating), while the cast iron case will bend or distort instead of cracking.

    A broken 84 k5 and lots of mud, it sucks to be me<P ID="edit"><FONT SIZE=-1>Edited by 84K5WITHAJUNK305 on 04/12/01 08:50 PM (server time).</FONT></P>
     
  4. CaptCrunch

    CaptCrunch 1/2 ton status

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    To add to what has been said... both trannys have their weak spots. A th400 would be bullet proof. Basically the first gear difference and the overdrive are the main differences... also 350's can be had either w/ or w/out a lock up converter... which gives better milage. The 700's can live a long and happy life w/ a few mods. Temp is the key... get the biggest cooler you can w/ big tires. Also don't skimp of the rebuild.... find a good shop that knows about 700's or you'll get screwed like a lot of the members have here. 700's are commonly screwed up worse after they are rebuilt and supposedly improved. TCI and Jet both make top notch 700's for perf as well as jw and 700r4 overdrives.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     

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