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Where to get the little vaccuum switch that controls the tranny?

Discussion in '1982-Present GM Diesel' started by afroman006, Apr 10, 2006.

  1. afroman006

    afroman006 1/2 ton status

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    I want to replace the little switch thing on the side of the injection pump that the vaccuum pump runs into, then down to the tranny. I have heard no one makes them any more but dont know for sure.
     
  2. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    I just bought one off of ebay from a guy in Texas. I noticed he had another one listed. Do a search for "6.2 diesel".


    Mike
     
  3. cegusman

    cegusman 3/4 ton status

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    I have them not to sure if they work, havn't run a auto in the k5 for a while. Pay shipping and there yours, or come done to katy and pick them up.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    I'm looking too..

    I have seen only 3 of them in junkyards..they wouldn't "break up" a running motor to sell me a "10 dollar switch" in all 3 cases...so my modulator is hooked straight to the vacuum pump for now..I did find 2 other switches used,but neither worked ..one had cracked hose nipples,the other one didn't work right either...I wish AC-Delco still made it..some parts stores say they can get it,but I''ve yet to see them...:crazy:
     
  5. AzzKicker

    AzzKicker 1/2 ton status

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    I had to do the same to mine as well. I just did direct hookup and tranny actually shifted ok. Better than the hard SLAM INTO 2nd it used to do.
     
  6. afroman006

    afroman006 1/2 ton status

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    Ok well I finally got a replacement tranny swapped into my trail truck so I need to revisit this modulator issue. I tried hooking an adjustable modulator directly up to the vaccuum pump on my last tranny and I adjusted it a little. It shifted really soft (which I know is bad for the tranny) but it did shift. Then the tranny started slipping and was pronounced dead. The guy I bought it from is prety shady so it was probably in prety bad condition to start with but I dont want to worry about killing my current tranny by hooking up the modulator incorrectly.

    I took the new tranny for a test drive today and it blew my mind when the tranny shifted into 2nd and 3rd, and the modulator wasnt even hooked up at all! It shifted late and hard (which I hear is "better" for the tranny), but it did shift and worked at 100%. I would like to go ahead and hook up the modulator correctly so I need to know how to. I assume the magic gizmo we are discussin is the plastic thingy on the passenger side of the IP with the two hose nipples on the top of it right? I figure one nipple goes dirrectly to the vaccuum pump and the other goes to the modulator, but which is which?
     
  7. jarheadk5

    jarheadk5 1/2 ton status

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    I'm gonna scan the relevant pages from my 6.2 manual and post 'em in the sticky 6.2 tech info post I have.

    **EDIT** My freakin' scanner's not working right now...

    The vacuum source (the pump) gets hooked up to the inboard nipple, and the modulator gets hooked up to the outboard nipple.
    In the drawing, the "inboard" nipple appears to be the bottom nipple, and the "outboard" nipple appears to be the top nipple.

    The GM part number for the updated VRV (vacuum regulator valve) is 14057219. Dunno if GM Parts Direct has this listed or not; don't have time to check right now.

    There's a procedure for setting the valve correctly, but it's a bit long-winded, and it's late, and the wifey is calling for me to come to bed. I'll type it out if I can't get the damn scanner to work tomorrow.
     
    Last edited: Jun 12, 2006
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    yup...

    Its just a valve that tapers off the vacuum at higher throttle openings..not sure if it matters which hose goes to the pump or not..my guess is it doesn't really matter,since it just interrupts the vacuum....

    I've been thinking a small regular ball valve could be modified to bolt up and work just like the OEM switch...if I cant find a good used or new switch,I might try cobbing one up!...I'm unsure if running my modulator direct is harmful or not,but I cant leave mine dissconnected...I tried!

    ..if I do,it wont shift into 2nd until 35 mph,and 3rd at 50+ mph,and the govenor kicks in on the injector pump,and shuts the motor down momentarily!..that CANT be good for the motor OR tranny,and it sucks fuel down three times quicker..(I've had mine running direct vacuum from the pump to modulator,with its adjusting screw turned IN all the way,for about 2500 miles,mostly plowing miles and winter use,and the tranny seems just fine,no slippage so far..but I have nightmares about it burning up..:crazy: )...
     
  9. afroman006

    afroman006 1/2 ton status

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    The governor shuts the motor down? I always thought it just stopped it from accelerating any higher. I have burried the throttle to the floor on my trail truck more times than I can count and it just revs up and stays there.

    Thanks for the info jarhead if I'm lucky the switch that is currently on my motor will work and the only other thing I'll need to do is hook up the kickdown switch.
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    ....

    On my truck the govenor seems to shut the fuel off,causing the engine to bog like the key was shut off...as soon as the RPM's fall to a safe level,it comes back to life..not sure it this is how they all act..maybe my fuel filter is plugged up some,I haven't changed it since I got the truck..but have driven it only a few thousand miles,and the filter looked new..at any rate,I'd rather have it do that,than toss a rod thru the block!:eek1: :doah: ..

    I'm going to try searching for that GM part # that Jarhead posted..hoping someone still has one in stock somewhere...:crazy:
     
  11. afroman006

    afroman006 1/2 ton status

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    I looked on GM parts direct last night and it appears they do have that part # jarhead provided, but its $60. I hope mine works...
     
  12. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    can someone post a pic of this modulator? i'm not sure if mine is missing, but i'm getting rid of my auto tranny, so i could part w/ my modulator for cost of shipping if i still got it. :)
     
  13. diesel4me

    diesel4me 1 ton status Premium Member

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    only used on...

    They are only used on diesel trucks with a TH400 (or TH350,if GM ever put them behind a diesel)..the 700R4 doesn't have a modulator,and doesn't need one... I'm hoping to score one off a junker one of these days at the scrapyard..60 bucks buys a lot of groceries and beer!..(but I guess it IS cheaper than a new tranny!)....:crazy:
     
  14. cegusman

    cegusman 3/4 ton status

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    The 6.2/700r4 did have one,. I remember taking my off when I switched to a manual.
     
  15. diesel4me

    diesel4me 1 ton status Premium Member

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    hmmm..

    Well,a 700R4 has no modulator,so if they put that switch on trucks with a 700R4,it must be to run the EGR or EPR valve--I think mine has more than one port for vacuum hoses to hook to,so maybe the EGR and EPR valve also gets vacuum from that switch (both are dissconnected on my truck,they were when I got it)....:crazy:
     
  16. jarheadk5

    jarheadk5 1/2 ton status

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    Still want me to scan the relevant pages out of the manual for ya?
     
  17. afroman006

    afroman006 1/2 ton status

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    Yah that'd be great thanks.
     
  18. jarheadk5

    jarheadk5 1/2 ton status

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    OK, I'll get them scanned before the end of the night and post 'em in the "6.2 Tech Info" sticky post.
     
  19. jarheadk5

    jarheadk5 1/2 ton status

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    Well, not quite "before the end of the night"... but they're up. Enjoy!
     
  20. afroman006

    afroman006 1/2 ton status

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    Sweet thanks.
     

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