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manual lock up 700R4?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by CHEVY 4WD, Jul 12, 2003.

  1. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    ok next drive line project is the tranny I want to just start over witha bowtie overdrive stage 3 700r4 (the truck already has a 700r4) Im gonna put a big cooler and deep pan on it but I want to run about a 2200-2400 stall converter. But I dont wanna get it real how so what my question is how would you make a 700R4 have a manual lock up?
    BTW is it a wise chose to go with a bowtie overdrive over a B&M or anyothers?
     
  2. BobK

    BobK 1/2 ton status

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    Go to Bowtie's site.They have the info. there.Wireing schematics and how it works.
    click here
     
  3. Blue85

    Blue85 Troll Premium Member

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    If you request it, they can easily set it up for manual converter lock. However, I recommend that you still have some automatic controls, especially for 4th gear, so that you can't forget about it and cook the tranny.

    There are different ways to wire it and that is all easy to change later. The important decision is what to put in the valve body. There is a valve that reads TV pressure and governor pressure and decides whether or not the converter should be locked. The pre-ECM trucks used this along with a manifold vacuum switch to control lockup. ECM trucks have lockup controlled entirely by the computer. In these setups, you already have a manual lockup option just by wiring in a switch.

    I use the older style (hydraulic + electrical lockup signals) with a bypass switch in the cab to prevent lockup below 4th gear. I can't think of any good situation to have the converter unlocked in 4th gear.

    The problem with full manual control is that the lockup clutch is not that tough. If you shift gears and hammer down on the throttle with it locked, you can wear it out pretty quick. For full manual setups, you should think about one of those high $$ converters with a big clutch. Remember that the transmission has to be pulled everytime the converter is changed. And if the clutch goes bad and you don't notice it for a while you can smoke the whole tranny.

    It goes without saying that you need a tranny temp gauge.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I concur with the "stock" setup. I like things being computer controlled for the most part (or at least monitored) but my '83 with no ECM locked up "perfectly". I see no reason not to run a stock vacuum/VSS locking converter setup if you have an '81-87 truck, or, as long as you don't care what the speedometer looks like, in a '73-80(or so) truck.

    Only reason to run manual lockup IMO (since the above is such an easy option) is if you simply can't stand to make the VSS work right. I'm sure it can be done with only vacuum, but I liked knowing it wouldn't lock at low speeds, the 305 was a dog as it was.
     
  5. Chris_T

    Chris_T 1/2 ton status

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    I have a manual un-lock on my 700 .. works good ... keeps the convertor locked in OD unless I manually unlock it. Keeps it from locking and unlocking at rpms which are just on the bubble or long hills, but if I want it to unlock rather than shift down (say you're just about to crest that hill) I flip the switch for a few seconds and it runs unlocked.

    I also have a Trans temp guage in case I'm ever a bonehead and leave it unlocked, but I can tell just driving if it is locked or unlocked in OD.
     
  6. Chris_T

    Chris_T 1/2 ton status

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    OK correct me if I'm wrong, but are there not separate valves in the valve body that differentiate lockup vs unlocked for each gear?

    I didn't mention this in my previous post, but mine only locks in OD. 1st, second, third, it doesn't matter what the switch is set at, it doesn't lock.
     
  7. BobK

    BobK 1/2 ton status

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    There is a preassure switch in the valve body that will ground out the TCC(transmission converter clutch) solenoid and activate it once that preassure switch reaches a predetermined line preassure in 4th.
    Does that make sense?

    Basically once the switch reads a certain preasurre it will complete the TCC solenoid circuit and the T/C will lockup.
    It can be wired to bypass that 4th preassure switch with a toggle switch.This will allow the T/C to lockup in 2nd,3rd + 4th if you wanted it to.
     
  8. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    well im gonna run a tranny temp gauge and hopfully a dummy light too. But the main reason I even what this is because I want to have a 2400 stall and still be able to cursie down the road at 2200 with out heating up the tranny.
     
  9. BobK

    BobK 1/2 ton status

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    Well when the T/C is locked up it's a solid connection between the trans and motor.No slippage of the T/C when locked up.No slippage = reduced heat.
     

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