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TH350 vs. TH400....got a fix, need to decide.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BLzr4x4ngkid, Apr 2, 2001.

  1. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    What's the difference? I had a TH350 in my Jimmy and loved it. Hopefully my truck is going into the tranny shop here in a day or so. I don't really know the differences between the two, but have heard there isn't much. Since I'm going to go ahead and have a new tranny put in, I want a 350 or 400. Let me know ASAP. See ya!

    "Don't hit me with them negative waves so early in the morning." Odd Ball--Kelly's Hereos
     
  2. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    If it won't take too much mod- Go for the 400 !
    The TH400 is a much tougher tranny with bigger clutch discs etc., Look at my post to Riz about what else to add. DON'T go stock, add a shift kit etc. The TH400 I put behind my old days hot rod actually barked the tires between 1st-2nd and 2-3rd.

    [​IMG]
    [​IMG]<font color=red>Rid'in High In My K5[​IMG]
     
  3. HarryH3

    HarryH3 1 ton status Author

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    The Turbo 400 is a stronger tranny, but a properly built Turbo 350 will take a lot of abuse. Keep in mind that to install the Turbo 400 you will also have to change the input shaft on your transfer case, get the correct adapter to go between the trans and transfer case, then shorten the rear driveshaft and lengthen the front one. You'll also have to install the kickdown switch required for the Turbo 400. So add $500 or so, plus labor, to do the swap.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  4. '73 K5

    '73 K5 1/2 ton status

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    Dude, that sucks. I smoked 2 TH350's in my second Blazer. I even had a temp gauge for the tranny so I would know when to stop 4 wheeling and let it cool down...it still didn't help. Thats why the next Blazer I got had the 4 speed manual. Go for the 400 if you can.

    '73 K5
    Chevy good...Ford bad
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    Just an added note to what others posted.... The 400 has a higher first gear than the TH350...

    The first gear in the TH350 is 2.52:1 and the TH400 is a 2.48:1.. Not sure if anyone could really tell the difference though... The th400 is a stronger tranny though!!!

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; <A target="_blank" HREF=http://emmett.coloradok5.com>http://emmett.coloradok5.com</A>

    "He who uses a winch...... Is tired of yankin!"
     
  6. CaptCrunch

    CaptCrunch 1/2 ton status

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    I agree w/ harry... 400 is stronger, but a 350 these days can be built really stout and tough! With the mega tire you got I'd probably say a 400 is a good idea if $$$ allows... Otherwise a built 700 or 350 done right will be ok... might just wear out a bit quicker. Shift kits are much safer in 350/400 trannys, but talk to your tranny guy... if he is knowledgable enough he maybe able to get it to a happy medium w/out one and using his own knowledge.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  7. prjt_blzr

    prjt_blzr 1/2 ton status

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    Been there done that. I started with a TH350 behind a 455 buick, 4:10 gears and 35" tires on my K5. I toasted the tranny in 12 months. This was a professionally built TH350 that was SUPPOSED to live behind a big block. I wound up driving 5 miles home in reverse. I've run a TH400 for the last 12 years. No failures!! Go with the TH400 if you can afford it.
     
  8. ftn96

    ftn96 1/2 ton status

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    Go with the 400. There is a kit which includes everything you need at http://www.nashvillek5.freeservers.com
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    ROTFLMAO!!! [​IMG] That's like in the movie License to Drive when the kid drives mom to the hospital in reverse LOL [​IMG] You must of gotten some funny looks... Another option is a TCI 350 trans... Have a guy I know running that in his drag car and seems to be living alright... but a 400 is by far the strongest.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  10. muddin4fun

    muddin4fun 3/4 ton status

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    True...a TH400 is a stouter, heavier duty tranny, but it is geared lower so it takes away from gas milage. A TH350 is a good all around tranny that is pretty tough stock and can be built to do anything you want. It just depends on what you'll do with it. I think if you are doing serious mud bogs, serious rock crawling, or towing loads that need a one ton truck (we all overload our blazers cause they can handle it [​IMG]) then I would op for the TH400.

    [​IMG]


    <A target="_blank" HREF=http://muddin4fun.coloradok5.com>http://muddin4fun.coloradok5.com</A>
     
  11. thatK30guy

    thatK30guy 1 ton status Premium Member

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    If I were you, and on a budget, then get a built 350. The 400 wont bolt up to your t-case because the shaft is bigger around and has 32 splines. The 700 and 350 both have the same size shaft and 27 spline count. This would make it easier to get back on the road faster while reusing your same driveshafts also.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Everyone has covered everything except parasitic loss. The 400 will cost you HP compared to a 350. It does all depend on application. My friend runs his high 12 drag car (and sometimes street car) with a TH350. has been for a couple of years. Proper buildup has a lot to do with it.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  13. prjt_blzr

    prjt_blzr 1/2 ton status

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    More details. Rush hour traffic in Hartford CT. It was entertaining to see the look on peoples faces that were facing the front a K5 with 6" lift and 35's. I don't think they knew if I was coming or going. It did save a costly tow and a 2 hour wait for the tow truck.
     

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