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No OD in my 700-R4

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 83ZZ502_Jimmy, Dec 3, 2001.

  1. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    The 700-R4 in my new to me 87 K-10 stopped working properly. The trans shifts fine but will not go into OD. I checked the fluid, nice and clean. The linkage seems OK. The TV cable feels and looks OK.
    What's wrong?

    Thanks in advance,
    John

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  2. Blue85

    Blue85 Troll Premium Member

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    Sometimes a torque converter lock up problem will look like a no overdrive problem. The slip in the converter is relative to the torque through it. The power needed to push the truck at a given speed is fixed, so slowing the engine down by upshifting increases the torque that it must produce. Because of this, the engine rpm is sometimes similar in 3rd and 4th gears with the converter unlocked, especially if your stall speed is a little higher than stock.

    Test to see if the lockup works by cruising down the highway and just barely pushing in on the brake pedal. This will unlock the converter, so the rpm should go up and then go back down again when you release the pedal. If nothing is happening, you don't have lock up. It could be that a fuse is blown, the brake pedal switch needs adjustment or your L/U solenoid has gone bad. L/U clutches in converters can go bad, too.

    If it is an O/D problem:
    The band that is applied to shift from 3rd to 4th is the same band that is used for 2nd gear, so that band must be OK. It could be the 3-4 shift valve sticking or you may have a bad seal on the 4th apply piston. There are two pistons in the servo, one works in 2nd gear and the other works in 4th, so they can go bad independantly. A stuck or improperly adjusted TV cable (or valve) usually makes all of the shifts wrong or nonexistent.

    <font color=green>Oh man, 4:10's are sure better than 3.08's!</font color=green>
     
  3. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    It is not the TCC. It is locking up just fine. When in OD the trans runs fine in 3rd but wont shift. It will like "coast" when you take your foot off the gas. Then it will "catch-up" when you step on it again. Is this a hrad fix or something that can be fixed w/out a lot of expense?

    Thanks,
    John

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Coasting and catching up doesn't sound like the convertor is locking to me...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  5. muddin4fun

    muddin4fun 3/4 ton status

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    is there a little solinoid or valve that controls when it goes into OD? Maybe if something is gooped up in there, the tranny might think you have it floored and won't go into OD. *shrug*
    When I had a pickup with a 700 in it, I was looking into getting a replacement part so I could cruise above 70 without it shifting out of OD. Maybe something is wrong with that part?

    Don't hit me, Mr. Moderator... I'll go back on topic... I swear![​IMG]

    <a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>
     
  6. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    It locks in D. B/C when i step on the brake at 55-60 mph I can hear/feel it unlock. the RPM's go up. I could be wrong but I think it is locking.

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  7. Blue85

    Blue85 Troll Premium Member

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    Your "coasting and catching" almost sounds like it is shifting in and out of 4th gear. Can you get it to do the same thing in D instead of OD?

    If that's the case, then something is triggering the 4-3 downshift too soon. If so, then the problem is more than likely somewhere in the valve body.

    If it never goes into OD, that could be a lot of different problems, but it is probably solveable without pulling the slushbox.

    You have of course verified the fluid level and condition, right?

    <font color=green>Oh man, 4:10's are sure better than 3.08's!</font color=green>
     
  8. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    IT wont do the same thing in D. It works fine in D and in in OD but wont go into OD at all.

    It is really beginning to aggravate me.
    Thanks for all the help.
    John

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  9. 90K5

    90K5 1/2 ton status

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    Mine acted like that, but it lost 3rd too, had to have it rebuilt

    90K5
     
  10. Chris_T

    Chris_T 1/2 ton status

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    what about an overly tight detent cable? not allowing it to stay in 4th?
     
  11. shawnboy

    shawnboy 1/2 ton status

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    Reset the the tv cable anyway. If the problem persists go to a reputable tranny shop for a diagnostic. Anyone but aamco should be fine.
    Shawnboy.

    <font color=red>If you are having too much fun it's probably illegal.</font color=red>
     

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