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Benefits of manual valve body on auto trans.?

Discussion in 'The Garage' started by mtn. burb, Apr 28, 2005.

  1. mtn. burb

    mtn. burb 1/2 ton status

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    I noticed a couple of rigs on line lately running an Art Carr manual valve body, or reverse manual valve body on TH400 tranny's.

    So you can stay in the desired gear you want on the trail, but have to shift up / down on the street.

    What's a reverse manual valve body do - change the shifting pattern?

    What am I missing here? What's the big benefit?
     
  2. originalspanksta

    originalspanksta 1/2 ton status

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    std= PRN321

    Rev= PRN123

    nicer to go from 1st to reverse, nothing inbetween but neutral. And you have to make EVERY shift.
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    They allow you to pick your gear. If you have the shifter in 3rd gear with a manual valve body it is in 3rd gear only and will not shift to second or first. If you want to be in 1st gear or 2nd gear you must shift to that gear.

    With a manual valve body the gear you are in is the gear you are in until you shift it like a manual tranny. The only difference is you don't have to push the clutch to shift gears.

    The nice part about that offroad is you can choose the gear that is right for the terrain.

    Marv Springer has a manual VB TH350 in his buggy. It has a doubler and a beefy 454. Most of the time he keeps the tcase in double low and if he doesn't need that low a gear he just uses 2nd gear in the tranny.

    On alot of obsticles he uses 2nd gear and double low. It allows him to crawl most average obsticles with more control then 1st gear. With a torquey 454, deep gears, and light weight of the buggy 1st gear double low can have to much power to control. It is harder to finesse the obsticle in 1st gear then 2nd in his buggy.

    The motor has so much torque and is kinda touchy because of the fuel injection that it is easy to get the motor to spin up the RPM band to fast and make life a PITA offroad.

    I have a similar problem in my truck with the touchy FI system and deep gears. It likes to jump off idle and the TPI tires to spin up the RPM band quickly. I don't have the manual valve body and it sucks let me tell you. Life offroad for me is all about the brakes. Your stand on the brakes and bring the RPM up to about 1000RPM and left off the brakes until it crawls right up.

    Lately in AZ it has been real wet on the trail from rain and it makes life for me a Mofo because the motor has so much torque right of idle and the gears are so low. A manual valve body will be in order for me when I install my TH400 down the road.

    Harley
     
  4. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    I just picked up my new TH-350 today from the tranny guy. I had a reverse manual valve body installed along with a total rebuild. :D

    Benefits of the manual valve body:

    1) NO FREAKIN MODULATOR VALVE! Meaning, nothing there to fail in the automatic portion of shifting, and no stupid vacuum lines to leak or tear off on the trail.

    2) No detent cable to wear out or become unadjusted. There's no longer an automatic passing gear, so the hole is simply blocked off.

    3) Pick a gear and go. Whatever it's in, it's there. Mine has a safety feature installed that will let the tranny "freewheel" if it is down-shifted from 3rd to 2nd, meaning no 10,000 RPM accidents or tire flat-spotting squeals as the tranny tries to slow the truck down.

    Benefits of a reverse valve body:

    It's only REAL benefit shines is if you have said manual valve body installed. It allows 1st gear and reverse to be a close pattern. See below

    Factory setup (TH-350):
    P
    R
    N
    3
    2
    1

    Reverse Manual Valve Body:
    P
    R
    N
    1
    2
    3

    See, for offroad use, it allows quicker and, should be, less missed shifts.

    It's really all preference as to whether or not you use the reverse pattern with the manual valve body. There's no real benefit to it IF you know what you're doing other than keeping it simple and straight-forward.
     
  5. mtn. burb

    mtn. burb 1/2 ton status

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    Thankyou all very much.

    This is why I am a member here.

    I got three intelligent, helpful, well written replies to a question in which I was clueless about.

    Cool. Now if I have to pull my tranny to replace the output shaft for the Doubler ( ordered this week from Steve ) I will consider a manual valve body.

    :waytogo:
     
  6. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    cool post big orange... sounds like a manual valvebody tranny would be more reliable. might have to think about that when I rebuild my 700R4...

    j
     
  7. 70~K5

    70~K5 1/2 ton status

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    A reverse valve body keeps 3rd gear away from neutral. They 1st gained popularity in drag racing as you won't miss 3rd gear and go into neutral by mistake. The same would apply to mud or sand drags too. ;)
     
  8. originalspanksta

    originalspanksta 1/2 ton status

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    You may not need to pull the tranny for your doubler, there are 2 options, you either replace the output shaft, (like you said) OR someone sells a spacer to go between the trans case and the t-case adapter that takes up the extra 1 1/8" of output shaft that needs to be accounted for.
     

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