Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

th350 to 700r

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by kiley, May 9, 2001.

  1. kiley

    kiley Registered Member

    Joined:
    Mar 5, 2001
    Posts:
    87
    Likes Received:
    0
    Location:
    Salem, Oregon
    I don't know much about transmissions so forgive any incorrect wording, etc.

    What is everyone's opinions on swapping a th350 for a 700r? Goal number one is to get a lower 1st gear for going downhill (kinda scary right now). Goal number two is to get better fuel economy. I know it won't be a huge jump but anything helps. Is the expense and trouble worth it or would a doubler (spendy) be the better option? The obvious answer would be both but who has that kind of money?

    72 cst
     
  2. Roostr84

    Roostr84 1/2 ton status

    Joined:
    Aug 19, 2000
    Posts:
    451
    Likes Received:
    0
    Location:
    NJ
    Well here is the deal with the swap. The easiest way in my opinion would be to get the output shaft from advance adapters tear down the 700r4 install it and then everything would line up. Otherwise you would have to buy the 700 dollar adpater that requires you to move the drivelines too. The shaft is about 100-130 bucks, add that to the cost for installing it, plus you will want to beef up the trans anyway as they are notoriously failure prone. If you haven't bought one yet look for an 87-up one as it has the updates the early one lacked.
     
  3. Steve_Chin

    Steve_Chin 1/2 ton status

    Joined:
    Mar 6, 2001
    Posts:
    1,126
    Likes Received:
    0
    Location:
    Foster City, CA, USA
    On a side note, you're not going to get much more in the way of compression braking from the 700-R4 than from the TH-350. The major problem in trying to get either of those transmissions to brake for you is the torque converter. The problem is worse if you have a "performance" torque converter, as they slip more than the "fuel economy" type torque converters.
     
  4. kiley

    kiley Registered Member

    Joined:
    Mar 5, 2001
    Posts:
    87
    Likes Received:
    0
    Location:
    Salem, Oregon
  5. Roostr84

    Roostr84 1/2 ton status

    Joined:
    Aug 19, 2000
    Posts:
    451
    Likes Received:
    0
    Location:
    NJ
    Well to tell you the truth unless you are swapping for another reason ( ie you need a new trans the milage is not worth the cost unless you are getting a good deal. This is agreed upon by most experts who perform these swaps as well. The benefits are gonna be in less wear and tear on the motor, and better ratios on the trail as well as in first gear off the line or towing. You will realize benefits in milage but not enough to warrant the cost alone.

    Chris
    www.roostr84.coloradok5.com
     
  6. Steve_Chin

    Steve_Chin 1/2 ton status

    Joined:
    Mar 6, 2001
    Posts:
    1,126
    Likes Received:
    0
    Location:
    Foster City, CA, USA
    You aren't going to get much better gas mileage, if my 5-speed swap is any indication. I did the swap partially for the "gee-whiz" factor (kind of a big factor!) and partially because I wanted synchronizers in every gear vas. the 4-speed. You don't have to worry about the synchronizer part because you have an auto, so the gee-whiz factor would be the big thing (unless your current tranny is almost dead).
     
  7. kiley

    kiley Registered Member

    Joined:
    Mar 5, 2001
    Posts:
    87
    Likes Received:
    0
    Location:
    Salem, Oregon
    Thanks guys. Your information is invaluable. My current tranny is just fine so I'll stick with what I have and save up for a doubler!
     

Share This Page