Tranny Upgrade~ 350TH to 700r4

Discussion in '1967-1972' started by vwnate1, Feb 26, 2012.

  1. vwnate1

    vwnate1 Member

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    Anyone here done this ? .

    Pitfalls ? .

    Will I need a different crossmember ? .

    How to recognize the 700r4 tranny when I'm in the junkyard ? .

    TIA ,
     
  2. ol' chebby

    ol' chebby Member

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    I just put one in mine less than a year ago. I got lucky and had the long tailshaft 350 already in my truck....the 700 is identical! For the short shaft 350, the 700 is 2-3" longer and the crossmember moves back about the same. I would think you could just redrill the holes for the crossmember in the frame rails and slide it back. You will also have to shorten the driveshaft. The 700 is well worth the swap.
     
  3. vwnate1

    vwnate1 Member

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    1St. Reply

    THANK YOU ! .

    I have no idea what TH350 I have now , I'd also like to hear what vehicles to look for with this tranny when I'm junkyard shopping .

    Pix would be good .

    Can I re use the same crossmember ? .

    No worries on the driveshaft as it has the original U-Joints (no Zerks) so I needed to yank it for rebuilding anyways .

    Keep the tips , hints and conversion stories and warnings coming please ! .

    .
     
  4. ol' chebby

    ol' chebby Member

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    Most gm cars and trucks from the mid 80s with OD are 700r or 200r. Do a search as there are more desireable years. I may have one coming available soon from the 60 Dodge project truck, it has a 350/700R combo coming out. I also have a local builder who can build it up for $400......CHEAP and RIGHT, He does all of our trans. work.
     
  5. vwnate1

    vwnate1 Member

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    Trannies

    THANX ! .

    I have heard the 200r is O.K. too , as this will be a light duty if high mileage truck , maybe that'd be O.K. .

    Too bad you're so far away :( prolly cost too much to ship to me here , even By Greyhound .
     
  6. ol' chebby

    ol' chebby Member

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  7. vwnate1

    vwnate1 Member

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    TH350 Lock Up

    Thanx ! .

    I see they offer a lock up torque converter option on their rebuilt TH350 , including the torque converter it's $1,500 , sounds maybe this is the way to go as it'd bolt in to my current cross member .

    Do you know , off hand , what the stock TC stall speed is ? I'm very happy with whatever it is now , stall speed wise .
     
  8. ol' chebby

    ol' chebby Member

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    I would say 1500 max. That is what mine was.
     
  9. vwnate1

    vwnate1 Member

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    Stall Speed

    Thanx , I was figuring about that but would like to know .
     
  10. bubba_t87

    bubba_t87 Member

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    I too was thinkin of swapping in a 700r4 I have in the garage into my 72. the tranny is out of an 87 monte carlo, so my concerns is if it will work, and if it will withstand the horsepower I have in the engine.
     
  11. vwnate1

    vwnate1 Member

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    Tranny Upgrade

    Yes , it's do - able , just be aware you'll have to move the cross member back a bit and shorten the driveshaft , run some new wires etc.

    This is why in the end I decided to go with a TH350-C , it's only a lockup torque converter on a TH350 but they build up the TH350 so it'll handle mucho horsepower .
     
  12. ol' chebby

    ol' chebby Member

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    With the 700 and a 3.08 rear, 29" tall tires, I'm tooling down the highway at 65 turning around 1900RPM. I averaged 17MPG coming back from the beach a few weeks ago.
     
  13. vwnate1

    vwnate1 Member

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    Too Late !

    As my rebuilt TH350-C came , we picked it up Wednesday after work .

    I'm averaging 16 MPG's now @ 65 MPH & 28" tires....

    I sure do use a lot of oil though ~ I'll send the cylinder head out soon , I heard about some old Guy in a Machine Shop who actually knows how to properlydo L6 heads and isn't above working on lowly 6 - Bangers .

    Trick is , I managed to lose his 'phone # :( .
     

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