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Telling a TH350 from a TH400

Discussion in 'The Garage' started by AZOffroad, Feb 12, 2006.

  1. AZOffroad

    AZOffroad Registered Member

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    I bought a '78 Blazer today (Bonanza/Cheyenne) with the 400ci motor. I owned an '89 and a '90 Blazer previously, but am not at all familiar with the '78 era trucks. I looked up the specs on the '78 and was surprised to see that both the TH350 and the TH400 were offered that year. I had assumed all along that the truck has a TH350.

    How can I visually tell if I have a TH350 or the TH400?

    Also, while we're at it, how can I tell (visually) if my front axle is the D44 or the GM corp 10-bolt? (both were available in '78) I suppose if the D44 has more or less than 10 bolts, then it gets pretty easy to differentiate one from the other :wink1:

    Steve
    Gilbert, Arizona
     
  2. divorced

    divorced 3/4 ton status

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  3. DEMON44

    DEMON44 Low-Tech Redneck

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    I'm going to have to job my memory (or go outside and look at my truck) the 400 and 350 aside from case size have different pans. 400 pan kinda looks like texas. the vac modulators face different directions. 350 vac faces side 400 vac faces rear.


    D44 front will have a D44 cast into the pumpkin on the bottom driverside webbing. A D60 will have a D60 in that same spot. A corp 10bolt cover is round with 10 bolts. IIRC the corp 10 front wasn't offered until late '79/'80 model year, but could be wrong. Oh, that's only the pickup trucks, sorry. So could be either.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    ..TH350/vs TH400..a pair of Bonanza's!!..

    The TH400 tranny has the modulator up front near the bellhousing,faces the passenger side rocker panel,and the pan looks like a map of Texas,a boot heel imprint,or Illinois,depending on who you ask..its rare to see them in a 4x4 unless it was a 3/4 ton Camper Special ,or was ordered optionally when new..

    98% of them got TH350's,the modulator on those are in the rear of the tranny near the taill shaft on the passenger side..it faces the rear differential..has a square pan,with one corner cut off at a 45 degree angle..

    You might have a NP203 transfer case in a 78..it is cast iron and heavy,but its full time 4x4,and a chain drive,its not part time and gear driven like a NP205 is..a tag is on the front side up above the front driveshaft..it should say "New Process Gear" on it,and "NP 203" or NP205..you might have a TH400 with the NP203...I've seen a few of those,but only one NP205/TH400 combo.

    I have a 79 C-10 "Bonanza" pickup too!..dont see many "Bonanza's" around anymore..:crazy:
     
  5. supersize75k5

    supersize75k5 OrganDonorRacing.com

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    hey where in gilbert are ya!

    im over at val vista and warner, I drive this fugly orange tube truggy on the street quite a bit,

    as for if its a t-350

    look at the front passenger side of the trans, see if you see a kick down cable coming up right infront of the dipstick, if so, t-350

    -shawn
     
  6. AZOffroad

    AZOffroad Registered Member

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    I'm at Higley and Elliot. The K5 will be my daily driver, I'm retiring the CJ-7 to "weekend only" status.
     

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