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Need help from nailhead peps

Discussion in 'The Hokey Ass Message Board' started by Big Tony, Feb 27, 2012.

  1. Big Tony
    Joined: Mar 29, 2006
    Posts: 3,589

    Big Tony

    I have a 58 nailhead (364) that had a Dana junk tranny. I was told a TH 400 would bolt up, but seems that will only work with 59-64 models with out doing machine work on flywheel and starter work. So... My question is what tranny will bolt up easiest (automatic)

    Thanks in advance
  2. The end of the Nailhead era saw these engines fitted with GM's newest transmission, the Turbo-Hydramatic 400, and we bless those forward-thinking GM engineers, as this is a rare case of a vintage engine that comes with a thoroughly rugged, modern transmission! These were in '64-66 models, but then if you have a pre-1964 Nailhead, that '64-66 TH400 trans and flexplate can easily be fitted to the early (shorter) rear crank flange with an adapter from Centerville Auto Repair. Wilcap has adapters for GM automatics and a stick bellhousing.

    From Street Rodder Magazine
  3. Need to have a nailhead pattern turbo 400. 1964-66 nailheads have them. There is a difference in the torque converter snout size, but a simple adapter takes care of that. The internal parts are same as other turbo 400 trans, but the case is uniqu with the nailhead bellhousing pattern and distance.

    Added extra - 1964 was first year for the turbo 400 and has a single year only valve body, but it is still a good trans. 1965-66 are the same as all the rrest of the turbo 400 up through the years. So what does this mean for you? If you get a 1965-up the rebuild kit is cheaper. The basic hard parts inside are the same, it is just the unique valve body for 1964.
  4. There are only two bolt patterns on the back of these motors - 53-56 and 57-66.

    Sometimes you can find the nailhead case TH400 in 67-70 Jeep vehicles - needs a short tail cover and a specific yoke to convert to 2WD. They actually used it with an adapter behind Buick V6 and V8 engines for a couple years. We had one and my buddy scrapped the truck whole like an idiot.

    IIRC for 63-back motors you need to modify the flexplate a bit, there's a diameter change or something, a search of the HAMB or using Google to search the HAMB should bring it up.

  5. Switch-pitch converters are nice too.
  6. jrlemke
    Joined: Dec 20, 2009
    Posts: 83


    Measure the crank flange dia. and bore the flex-plate to that size. Make a "pilot bushing" to fit the crank hole (o.d.) and bore it to fit the converter snout. you can use steel for this 'cause it doesn't turn. I had the sizes at one time, but can't find them now. The starter should be o.k. I don't think I had to use the late starter. The rest is just hooking stuff up. As was said before,use the 64-66 trans if possible.
  7. DualQuad55
    Joined: Mar 5, 2005
    Posts: 1,377

    from Epsom, NH

    Just need to space the starter forward about 1/2-5/8" or the bendix will pass the ring gear.
  8. Dzus
    Joined: Apr 3, 2006
    Posts: 321


    The best bet these days for finding a nailhead th400 is under a jeep. They used them up to the mid 70's.
    I used to have one that was a buick 350/T400 combo, and it had the old nailhead case 400 with the BOP adapter ring in front of it like the pic in the lower left. You have to look close.
  9. IIRC 1972 they went to Chrysler for transmissions - but who knows what could have been left in a warehouse and used to build vehicles. I found out that 51-54 Chevy front wheel cylinders also interchange with Jeep for a couple years in the mid-70s.

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