TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale

Discussion in 'Chevy C/K Truck Forum' started by amcco220, Dec 15, 2013.

  1. amcco220

    amcco220 New Member

    I recently bought a 1978 Chevy C10 4x4 “Heavy 1/2 ton” 350 V8 Turbo 400
    “Less that 2,000 miles on crate motor and trans re-build” according to the sign in the window. Paid $3100 cash. Of course, about a month after I bought it, the transmission blew out.

    Now, I hadn’t been driving it too hard, just a few camping trips and used it to move. Probably only put another 500 miles on it. This truck is my hunting/camping/firewood truck, not my daily commuter. I do want it to keep it for a while and maybe eventually put some larger tires on it and a cap. So I want it burly/heavy duty, like it supposed to be.

    I hired a “mobile mechanic.” He came over and diagnosed the problem. He recommended we drop the tranny and bring it to a transmission shop, have them rebuild it, and then we put it back in at my house. Sounds good, but I had to diversify my options.

    So, I went on Craigslist and I found a guy who was parting out a late-80s 2wd Chevy van, the engine from which he had put into his 80-something Chevy truck. Turns out we shared the same profession, so I dont think he ****ed me over. But who knows? It is craigslist after all. I bought a working turbo 400 + torque converter for $250 from this guy.

    Anyhoo, the mobile mechanic and I dropped the transmission ONLY TO DISCOVER that when the truck was rebuilt they put a TH350 in it instead of a 400. The 350 looked like it had recently been rebuilt (or at least spray painted). My craigslist 400, however, was too long (by about 3 inches) to just be plopped in the truck and have me good to go.

    Now here’s my dilemma, do I:
    1) sell off the craigslist 400 turbo and bring the 350 into a transmission shop and have it rebuilt again, or
    2) Do I have the driveshaft modified and buy the necessary parts to have my truck accept a 400 (from a 2wd) and plop in my craigslist tranny?

    My main concerns are
    1) the dubious nature of a craigslist auto part, and
    2) did the 350 blow out because it was inadequate for the make & model of my tuck?

    (photos are of the truck and the craigslist tranny)

    Attached Files:

  2. BurbanMan

    BurbanMan Rockstar 3 Years 500 Posts

    Built 400 for hd use
  3. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    The TH400 is a stronger trans than a TH350, for your stated intentions and future plans I'd use the TH400.
    A guess would be either the p.o. faked a rebuild on the trans (for sale purposes, good luck proving it, but you do have the proof he wasnt truthful about trans model) or he had no clue what he had, or a bad rebuild, or he ragged the truck out and ran it to death.
    The TH400 will run slightly lower gear ratio than the TH350, but if a tire swap is in order this might work in your favor.
  4. zippstripp

    zippstripp Member 1 Year

    Check to make sure the TH400 will bolt to the TH350 transfer case. I think the TH400 has a bigger output shaft. If it will work use it and just have the drive shaft shortened.

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