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gas trnnies in a diesel?

Discussion in '1982-Present GM Diesel' started by marcus, Mar 28, 2002.

  1. marcus

    marcus Registered Member

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    Hi all,

    Well, my tranny finally bit the dust after a wheeling session last weekend. No more reverse...it's been coming for a while.

    Anyway, I have a couple of questions...I have found a rebuilt 700 (rebuilt about 10k miles ago), but it's from a gasser. The guy at the junk yard told me that you can't put a gasser tranny in a diesel, or else it keeps dropiing out of top gear...is this true? He also told me that tuning a gasser tranny to diesel specs takes a lot of work (change clitch pack, valve body...). Now I don't know alot about trannies, but this seems a bit far fetched....is it true?

    Also, I have a th400 lying around....is this a straight bolt in to a 1984 Blazer? I seem to remember that you need to lengthen/shorten drive shafts...I am thinking of putting the 400 until a suitable 700 comes along...before anyone tells me o keep the 400, I need the OD as I use will be using the truck on long distance drives

    Thanks for your help

    Mark
     
  2. René

    René 1/2 ton status

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    In my knowledge you must change only the governor naturally you need also the convertor from your diesel.

    To convert a TH700 by a TH400 to is not so easy. The driveshaft doesn't fit and for the transfer case another adapter is needed.

    Why don't you overhaul your own transmission?
     
  3. marcus

    marcus Registered Member

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    Rene,

    I just don't have the technical expertise to overhaul my own 700. Another problem is I am based in the UK, and the local tranny shop wants £1500 to rebuild it (2500 euros/ $2100!!!). I have found somehere who will fit a rebuilt transmission for £1000 (about $1300) which I am going to have to do.

    If you are offering to come over to the UK and strip / rebuild my tranny, feel free! I can offer you a roof over your head, , three square meals a day and as much beer as you can drink while you are doing the business!

    Mark

    ps anyone in the UK want to buy a TH400 box? Cheap!
     
  4. René

    René 1/2 ton status

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    That sounds very well, but I rather remain in Germany. With you the mechanics are still larger bandits than with us. Here you receive a transmission overhaul for 1300 Euros but it doesn’t helps probably…

    For the future change the ATF regularly and install the largest oil cooler you can find.
     
  5. arveetek

    arveetek 1/2 ton status

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    The diesel trannies do have a different torque convertor and a different governor.

    However, I've been running a 1990 model gasser 700R4 in my '81 for over six years now. It hasn't given me a single problem, and I do a lot of heavy towing.

    I like the higher shift points. The diesel governors make it shift too soon for my tastes.

    I bought my 700 from a salvage yard as well....they also kept telling me that it wouldn't work.....it had the electronic speedo hookup and all.....bunch of morons, really. Don't tell 'em what you're using it for, if the price is right, just buy it, and we'll make it work.

    Just make sure that 700 is built to the latest specs, and it has the 30 spline input shaft. The 27 spline units are the earliest and weakest.

    Casey
     
  6. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    I installed a gas transmiision in my 83 . I changed the governor and thats it !!!The trque convertor allows the enging to reach higher RPMs . What I would do is find a turbo 400 and replace the 700r4 .I did notice a big improvement in performance !!!
     
  7. René

    René 1/2 ton status

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    In my opinion the TH700 is strong enough. One must treat it only correctly. It has however two large advantages in opposite of the TH400 (also TH350):
    1. the shorter ratio in the first.
    2. the overdrive for a cosy cruise.
     

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