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Overall length of a TH400/NP208 VS 700r4/NP208??

Discussion in 'The Garage' started by diesel4me, Feb 7, 2010.

  1. diesel4me

    diesel4me 1 ton status Premium Member

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    Been looking at other options to put in my '85 K10 Burb (diesel) for a tranny--its got the 700r4/NP208 combo in it factory,and the tranny is losing overdrive and reverse after a good ride..time to fix it,or ditch it!.

    Was wondering if there is a chart that shows the overall length of different tranny/transfer case setups,or in other words,if there's any way to tell what other driveline combo's would fit without altering the driveshafts or crossmembers,etc..

    I had a line on a TH350 someone got from a car (short tail) and bought a spacer for the tail end,they claim that'll allow it to bolt right in place of a 700r4 with no mods to the shafts or crossmember..that would suit me fine,I dont drive far and could care less about losing the overdrive or the slightly lower first gear the 700r4 has..but I'd be faced with the issue of getting vacuum for the modulator valve on the TH350,(I have a vacuum pump,but lack the VRV valve it would require)--also the torque converter will only have 3 bolts ,not 6,but still bolt up,the stall speed is slightly higher too,being from a gas engine..

    So,anyone know what'll bolt up in place of a 700r4/NP208 without a bunch of headaches??..or should I bite the bullet and have the existing tranny fixed??..(I dont have much faith in the 700r4's to be truthful)..
     
  2. oatsk5

    oatsk5 1/2 ton status Premium Member GMOTM Winner

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    I may be wrong but i was told the diesel autos use a different pump.
     
  3. oatsk5

    oatsk5 1/2 ton status Premium Member GMOTM Winner

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    From the measurement i took they should darn close.
     
  4. rufusbooth

    rufusbooth 1/2 ton status

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    I don't think it is the pump it is the governor in the trans that is diesel specific in order to change the shift points to something that is more appropriate to a diesel.

    so in short you will need to do 2 things to make a different trans work.
    1. you will need the throttle valve that sends the proper vac signal to the modulator. Older 6.2s that ran the th400 have these.

    2. you will also nee the diesel specific governor for the th350 trans. Not sure if the th350 ever came in a diesel. Others will pipe up about it.

    Might be easier to rebuild the 700r and strengthen it up while you are at it. Built right, kept cool, and the TV cable set properly they are a reasonably strong trans.


    Rufus
     

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