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TH400/NP208 question...

Discussion in 'The Garage' started by diesel4me, Nov 25, 2005.

  1. diesel4me

    diesel4me 1 ton status Premium Member

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    Ok--my 82 K20 has a TH400/NP208 setup..
    I have a TH400 out in my shed,salvaged from a 1974 Monte Carlo that had a 454..it has the "short" tail on it,only about 4" long (approximately,eyeballing it)..it appears to me ,looking at the spare T/case and TH400 adapter I have in the shop,its possible it might be able to just yank the tail off the car tranny and use it on the NP208..looks like its "deep" enough to allow the shaft to slide in enough to bolt up..(or maybe I could use a spacer to take up the extra length,if its too long??--I realize the T-case would need to be shoved back to compensate,and possibly alter the driveshafts)..just wondering if anyone has done this.... :confused:

    Anyone know if its possible this would work?? :confused: --or should I put it up for sale on E-bay or something,since I need cash!..I'd hate to sell it if it would fit my truck as a spare,but I'd also hate to keep it and find out it wont work.. :doah: ..time to do some cleaning out around here..the 500 Caddy motor and its TH400 might be next ... :( ..
     
    Last edited: Nov 28, 2005
  2. diesel4me

    diesel4me 1 ton status Premium Member

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    Ttt

    So--nobody knows??? :dunno: :ears: ...
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Worst case, you could keep it as a spare and you'd just need to swap the output shaft from the dead tranny.

    It's a bit of work, but I don't believe any other GM tranny is as easy to disassemble as a TH400, and if you weren't replacing anything internal, it would go together quite simply.

    It seems like all the other output shafts seem to be just a hair too long, like 1/2" or so, and some have just trimmed the shaft.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    hmmm...

    Thanks!..I knew I could swap shafts,but I have never sucessfully gutted and rebuilt any automatic,so I would have a shop do it if it came to that..

    If the shaft was only slightly longer as you say,like 1/2" or 3/4" maybe,then I bet you could just add a spacer between the adapter and tranny,and there would be enough travel in the slip yokes on the driveshafts to let you move the T-case back and drill new holes for the crossmember..(use the cut off tail as the spacer?? :thinking: :laugh:

    I've seen 700R4's with a spacer in the junkyard trucks before -(I assumed someone used a car or 2wd tranny instead of a 4x4 one!)..

    It would be easier to cut off the excess shaft I suppose though,provided the splines are cut deep enough on the shaft to be able to go in all the way..I'd do it if I needed the tranny in a hurry!..maybe I'll keep that TH400,since it came off a 454,its probably a heavier duty one than usual.. :crazy:
     
  5. sweetk30

    sweetk30 professional hooker Premium Member

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    spacer could be a clocking ring also. and dont forget gm never used all the spline length to engage the tcase to tranny. .
     

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