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what kinda trany do i have?

Discussion in 'The Garage' started by vw62rag, Jul 7, 2004.

  1. vw62rag

    vw62rag Registered Member

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    i have jus got a 85 gmc jimmy and was assuming it had a th350 trans(the guy that sold it to me said it did) but i went to put a new filter n gasket on it and the oil pan is a square shape? i always thought a th350 had a pan that looked like a square with one corner hacked off.......? im a newbie /forums/images/graemlins/dunno.gif
     
  2. fortcollinsram

    fortcollinsram 1/2 ton status

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    th700r4

    Chris
     
  3. RaisedK5

    RaisedK5 1/2 ton status

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  4. vw62rag

    vw62rag Registered Member

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    COOL! thanks for the fast help! is this a good trany? i have a th400 out of a 3/4 suburban, should i consider swaping them?
     
  5. mechted

    mechted 1 ton status Premium Member

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    My understanding is that 700r4's are fine on the street, but you want to baby them offroad (or drop alot of money into upgrading them), if not avoid altogether
    th400s are great offroad, but no overdrive can kill gas mileage on a daily driver.
    So if you are looking at building a trail rig, most will say swap the th400 in, but if you plan on daily driving & trail riding, you need to think about it more (tire size, gears, engine, GVW, etc)
    this is just my opinion/understanding, someone with more knowledge will be able to respond more in depth
     
  6. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    How many miles are on it? Is it original? Rebuilt? It is for surely a th700 which IS a good tranny. I highly doubt it is original because the early stockers didn't last very long in the first place.

    In '84.5 they swapped in a larger 31 spline input shaft from the 27 spline unit. I would drive the truck and do what you will with it on and off road but just use common sense, if you are hard on something it doesn't matter what tranny you have, it will eventually give out. If and when it does let go here are a few things that need to be done if you plan on pushing some power and larger tires...

    *10 or 13 vein front pump
    *aftermarket converter with billet center hub instead of the stock cast converter that can snap with enough torque.
    *aftermarket sun gear(the stock one is patheticly thin)
    *better and more clutches in the 3rd and 4th pack.
    *late model planetaries( the early weak ones are the same as a th350)
    *A shift kit or corvetter servo
    *a big cooler plumbed in with the rad. cooler if you don't already have one stock.

    That would give you a reliable strong tranny that should be able to take almost anything you could dish to it without being stupid and last a long time in a mild to semi hardcore K5. I have the same mods as stated above and quite a few more because I wanted to make sure it would last behind my built 406SBC pushing 35" boggers at the truck pulls, mudding, etc. The only drawback to a th700 is the initial cost of building it isn't cheap, figure around $1500 or so for the upgrades stated above and even more with a few other upgrades I didn't list.
     

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