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700R4 vacuum adjustment

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 8_YOUR_H2, Mar 19, 2001.

  1. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Just befor I blew the head gaskets on my blazer the tranny would shift so hard between 1st and 2nd gear it would almost give whiplash but now that I have overhauled the motor it slips between 1st and 2nd. I was told this could be a vacuum adjsutment. where is this adjusted? I cant find it. Any help?
    Brent
     
  2. extremeblazer

    extremeblazer 1/2 ton status

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    700's use a throttle valve cable to increase or decrease main transmission line pressure in the transmission. This cable attaches to your carb or throttle body and is moved with the throttle. The more the gas is applied the more the cable moves and the more line pressure. The only adjustment is to push on a small tab on the cable bracket, this allows you to push the cable all the way in. You next pull the trottle wide open and the cable self adjust. If the cable is set incorrect the transmission could shift hard or slip. 700's do not have a vacuum control like 350's, so you won't find it. Try readjusting your tv cable it works every now and again. Also if the cable breaks the transmission creats really high pressure to keep from slipping and burning up. I saw a lot of this when I worked as a tranny rebuilder. I hope this helps.
     
  3. jimmyjack

    jimmyjack 1/2 ton status

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    700's don't have a vacuum line. Like Extreme said it uses a t/v cable or detent cable. It took me awhile to adjust mine. Lots of little trips back and forth to nowhere. I basically adjusted mine to where it "felt good". Not an exact science but my tranny guy told me he basically does the same thing. When all else fails let a transmission shop adjust it for you.

    creepin' and crawlin'

    Jim
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    The 700R4 uses what is called a throttle valve (TV) cable instead of a vacuum to regulate shift points. If you are facing toward the grille, the TV cable will next to carb below the throttle cable on the right. It moves with the throttle controlling a valve inside your transmission which regulates pressure, and your shift points. Try the search feature to get a detaied explanation buts its easy to set. Look at where the cable goes through the bracket on top the manifold. On the back of the bracked should be a plastic buttom shaped like a D. Push that button firmly with your thumb and grasp the bit of cable behind that button It should make a ratchetingise and pull all the way back to the firewall. Now with your thumb still on that button let go of the cable and pull the linkage for the throttle all the way like it was floor boarded (truck off of course!). If you're confused about the throttle linkage stuff, just a get a buddy to go in the truck and drop the pedal to the floor. Now let go of the button and bring the throttle back to normal. Take a test drive and make adjustments accordingly, closer to the firewall makes for higher shifts, further causes lower shifts. Thats how I've heard it done.

    I just pulled the cable back all the way to the firewall and took it for a drive, way to high of course. Moved it forward about three clicksand tried it, perfect shifts! Just make sure you rev slightly before it shifts and everything should kick butt.
     
  5. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Wow, I would have searched for days. I wondered why Chiltons and Hayes didnt mention anything about it!
    Thanks
    Brent
     

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